Turning tool for grooving polishing pad, apparatus and method of producing polishing pad using the tool, and polishing pad produced by using the tool

ABSTRACT

Disclosed is a turning tool for cutting circumferential grooves into a surface of a polishing pad formed of a resin material and utilized for polishing semiconductor devices. The turning tool comprising a cutting part arranged to have a tooth width within a range of 0.005-1.0 mm, a wedge angle within a range of 15-35 degrees, and a front clearance angle within a range of 65-45 degrees. A polishing pad effectively formed by using the turning tool, and an apparatus and a method of producing such a polishing pad by utilizing the turning tool are also disclosed.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a turning tool for producing apolishing pad made of a resin material and usable in the fabrication ofsemiconductor devices, especially for chemical mechanical polishing(CMP) executed for planaraizing surfaces of semiconductor wafers ordevices. The present invention further relates to a polishing padeffectively formed by using the turning tool, and an apparatus and amethod of producing such a polishing pad by utilizing the turning tool.

[0003] 2. Description of the Related Art

[0004] In the semiconductor fabrication processes, a substrate, e.g., asilicon wafer, may undergo multiple masking, etching, implantation, anddielectric and conductor deposition processes, to thereby form alamination of various kinds of thin layers such as metallic layers andinsulative layers. Between each processing steps, it is usuallynecessary to polish or planarize an outer or upper most surface of thewafer to obtain a substrate surface having a high degree of planarity.Chemical mechanical polishing (hereinafter referred to as “CMP”) is oneof known methods of planarization. CMP typically involves placing thewafer mounted on and rotated about an axis of a carrier against apolishing pad mounted on and rotated about an axis of a platen, andpushing the wafer against the polishing pad while supplying a polishingslurry at an interface between the upper most surface of the wafer andthe polishing pad. The polishing slurry consists of fine abrasiveparticles and suitable kind of liquid in which the abrasive particlesare dispersed. Typically, the polishing pad is made of a foamedrigid-resin material, so that a surface of the polishing pad has acellular structure of independent-cell type in which cells areindependent of each other or of open-cell type in which cells arecommunicated with each other, in order to facilitate conditioning of theslurry distribution between the wafer and the polishing pad.

[0005] Namely, the polishing pad for CMP is required to be capable ofevenly distributing the slurry over a substantially entire area of theupper most surface of the wafer that is to be polished, while preventinga stay or clogging of the slurry at a local portion of the upper mostsurface of the wafer. The polishing pad for CMP is further required tobe capable of promoting renewal of the slurry.

[0006] To meet these requirements, conventionally employed polishingpads for CMP are arranged to have polishing surfaces formed withrespective predetermined patterns, e.g., a pattern of recess or apattern of checked grooves intersecting at right rights. After a numberof polishing runs, the polishing pad having the pattern of recesses maysuffer from variation of diameter of the recesses, whereby the padsuffers from difficulty in exhibiting a desired chemical mechanicalpolishing effect with high stability. In the case of the polishing padhaving the pattern of checked grooves, a polishing condition is likelyto vary in the radial direction of the polishing pad, whereby the padsuffers from a high tendency of occurrence of uneven wearing of itssurface, resulting in uneven polishing.

[0007] Another known example of conventionally employed polishing padfor CMP is disclosed in U.S. Pat. Publication Nos. U.S. Pat. No.5,921,855 and U.S. Pat. No. 5,984,769. The disclosed polishing pad isprovided with a plurality of annular grooves open in its polishingsurface. The plurality of annular grooves are arranged in a generallyconcentric or coaxial relationship with each other, and are dimensionedto have a width of not smaller than 0.38 mm and a depth of not smallerthan 0.51 mm, and are uniformly spaced with a pitch of 2.29 mm in aradial direction of the polishing pad. However, the disclosed polishingpad suffers from inherent structural problems, namely, difficulty informing grooves extending in a circumferential direction in thepolishing pad and difficulty in ensuring a sufficient dimensionalaccuracy of the grooves.

[0008] More specifically described, the annular grooves may be formed onthe polishing surface of the polishing pad by embossing with a die, oralternatively may be formed by milling with a saw blade on a mill. Inthe former case, each of the formed annular grooves is prone to have adull shape, especially at its open-end edge portions, so that the widthof the groove varies in its depth direction. This causes undesirablevariation of the groove width, especially when the polishing surface ofthe polishing pad is worn or is conditioned by the dressing process,resulting in unstable polishing conditions. In the latter case, sincethe annular grooves are formed by milling of the saw blade on the mill,the formed annular grooves is likely to extend straightly to someextent, making it difficult to form a groove having a small width and asmall radius of curvature. This makes it impossible to form a desiredpolishing pad in which annular grooves having a relatively small widthare formed on a radially inner portion of its polishing surface as wellas a radially intermediate and a radially outer portion of its polishingsurface. In view of a recent tendency of employing a large-diameterwafer, e.g., a wafer having a diameter within a range of 200 mm-300 mmor more, the presence of useless area in the radially inner portion ofthe polishing surface of the polishing pad undesirably causes anenlargement in size of the polishing pad. Therefore, the problem of theradially inner useless area of the polishing pad becomes verysignificant.

[0009] Alternatively, the annular grooves may possibly be formed byturning with a turning tool. However, since the polishing pad is formedof a specific material having somewhat elasticity, e.g., a foamedrigid-resin material, it is significantly difficult to cut an annulargroove having a relatively small width and having a relatively smallradius of curvature into the polishing pad, with high dimensionalaccuracy. In the light of the physical property of the polishing pad,conventionally available tool for cutting a work piece made of metal ora rigid-resin material, are not suitable to cut the polishing pad. Forinstance, the tools for cutting the metallic or rigid-resin workingpiece are likely to interfere with the walls of each groove, therebypossibly producing burrs or other defects in the walls of the grooves.Thus, the conventionally available tools are incapable of cutting thesmall-width and small-radius grooves into the surface of the polishingpad having the somewhat elasticity, like the foamed rigid-resin members.

[0010] Moreover, the conventionally employed polishing pad disclosed inthe above-mentioned U.S. Patents has the generally concentric annulargrooves that have a relatively large width and are uniformly spaced atthe relatively large pitch. Further, the disclosed polishing padincludes a backside pad made of a compressed felt fibers leached withurethane, which has an elasticity larger than that of the polishing padand which is fixed the backside of the urethane pad. Thus, the disclosedpolishing pad is mounted on a platen of an optional CMP system via thebackside pad. This type of conventional polishing pad has been developedto be applied to planarization of a substrate having multilevelinterconnections in which metallic interconnect has a width of 0.25 μm,that is a most advanced technology at the time when applications for theabove-mentioned U.S. Patents were filed (i.e., 1997-1998). Namely, thetype of polishing pad has been developed to provide the substratesurface having a planarity at a level of 0.3 μm. In the light of thefact that the substrates having multilevel interconnections whosemetallic interconnect has a width approximately of 0.18 μm 0.15 μm and0.1 μm dominate the recent market, it is apparent that the CMP is nowrequired very sophisticated techniques, i.e., to provide the substratesurface having a high planarity at a level of 0.25 μm or lower. Thus,the conventional polishing pad disclosed in the above U.S. Patents isinsufficient for ensuring currently required polishing accuracy andpolishing efficiency, and accordingly is unsuitable to be used for CMPfor a planarization of a currently developed substrate of multilevelinterconnection, which includes interconnect metal layers made of a softcupper or gold.

[0011] In the conventional polishing pad disclosed in theabove-indicated U.S. Patents, the grooves having a relatively largewidth and the backside pad cooperate to allow a deformation of thepolishing surface, whereby the polishing surface of the polishing pad islikely to be deformed according to peaks and valleys in a surface of asubstrate to be polished, i.e., along with topography of upper mostsurface of the substrate. However, this surface deformation mechanism ofthe conventional polishing pad is insufficient to keep pace with thecurrently required level of polishing accuracy. In addition, the use ofthe backside pad, which is formed differently from the polishing pad,evidently has pushed up a manufacturing cost of the polishing pad.

SUMMARY OF THE INVENTION

[0012] It is therefore a first object of the invention to provide anovel turning tool for cutting circumferential grooves, e.g., amultiplicity of generally concentric annular grooves into a surface of apolishing pad formed of a resin material and utilized for polishingsemiconductor devices. The turning tool is capable of forming the finecircumferential grooves with a sufficiently small width and with highdimensional accuracy and high stability. The turning tool enables toform the small-width circumferential grooves in the radially innerportion of the polishing surface of the polishing pad, with ease.

[0013] It is a second object of the invention to provide a novel methodof producing a polishing pad formed of a resin material and usable forpolishing semiconductor devices, by utilizing a special turning toolconstructed according to the present invention. The method enables toform circumferential grooves, e.g., a multiplicity of generallyconcentric annular grooves on a surface of the polishing pad with asufficiently small width and with high dimensional accuracy and highstability, over a sufficiently wide area of the surface of the polishingpad including a radially inner portion of the surface of the polishingpad.

[0014] It is a third object of the invention to provide a polishing padformed of a resin material and usable for polishing semiconductordevices, which is novel in construction, which is suitably produced byusing a special turning tool specific working tool constructed accordingto the present invention, and which is effectively usable for chemicalmechanical polishing of a substrate of multilevel interconnectionstructure in which a width of a metallic interconnection is set to about0.1 μm.

[0015] It is a fourth object of the invention to provide a machine forforming grooves on a polishing pad, which is novel in construction,which utilizes a special turning tool constructed according to thepresent invention, and which is capable of easily cuttingcircumferential grooves e.g., a multiplicity of circumferential annulargrooves into a surface of the polishing pad such that the grooves have arelatively small width and spaced apart from each other with arelatively small radial pitch.

[0016] The above and/or other objects may be attained according to atleast one of the following aspects of the invention. The followingpreferred forms of the respective aspects of the invention may beadopted at any possible optional combinations. It is to be understoodthat the present invention is not limited to the following forms orcombinations of these forms, but may otherwise be recognized based onthe thought of the present invention that described in the wholespecification and drawings or that may be recognized by those skilled inthe art in the light of the disclosure in the whole specification anddrawings.

[0017] The above-indicated first object of the invention may be achievedaccording to a first aspect of the invention which provides a turningtool for cutting circumferential grooves into a surface of a polishingpad formed of a resin material and utilized for polishing semiconductordevices, the turning tool comprising: a cutting part arranged to have atooth width within a range of 0.005-1.0 mm, a wedge angle within a rangeof 15-35 degrees, and a front clearance angle within a range of 65-45degrees.

[0018] The turning tool of the invention comes into fruition as a resultof a large number of experiments and extensive studies on grooving of apolishing pad made of a resin material, which were conducted by theinventor of the present invention. In particular, the turning tool ofthe invention has been developed as a special turning tool capable ofcutting desired fine grooves with high dimensional accuracy into thepolishing pad made of the resin material in both of a solid state and afoamed state. One of the significant technical features of the turningtool of the present invention is that the wedge angle which is madesignificantly shape in comparison with general turning tools adapted tocut metallic work pieces, and the front clearance angle is madesufficiently larger than that of the general turning tools. Althoughsuch a general turning tool adapted to cut metallic work piece may beused for cutting work pieces made of rigid synthetic resin materials,such as engine plastics, polyamide resin, and the like, the generalturning tool is not able to process with sufficient dimensional accuracythe polishing pad made of the resin material whose hardness is smallerthan those of the rigid-synthetic resin materials. This clearly showssignificant difficulty or specialty in cutting the circumferentialgrooves into the polishing pad made of the resin material. Inparticular, the present turning tool enables to cut fine circumferentialgrooves with high dimensional accuracy into such a polishing pad made ofa foamed rigid-resin material, e.g., a foamed urethane pad, and apolishing pad made of a solid resin material whose hardness is generallysimilar to that of the polishing pad formed of the foamed rigid-resinmaterial.

[0019] The turning tool constructed according to the present inventionis capable of cutting into the polishing pad made of the resin materialthe circumferential grooves having a width of 1.0 mm or smaller, withhigh dimensional accuracy and without occurrence of burrs in the wallsof the grooves. Namely, the turning tool of the present invention makesit possible to stably cut the circumferential grooves into the surfaceof the polishing pad with a slight infeed rate, and to accurately formthe desired grooves in the very inner circumferential portion of thecircular work piece. It should be appreciated that the term“circumferential grooves” should be interpreted to mean groovesextending in a circumferential direction of the polishing pad, e.g., amultiplicity of generally annular generally concentric grooves, and aspiral groove or grooves. Preferably, the tooth width is held within arange of 0.1-1.0 mm.

[0020] The turning tool constructed according to the present inventionmay be made of known materials such as hard metal, high speed steel,carbon steel, ceramics, cermet, and diamonds. In the turning tool of thepresent invention, actual values of the wedge angle and the frontclearance angle may be suitably determined within the above-indicatedrange, taking into account a hardness or other specific physicalproperties of the work piece, i.e., the polishing pad made of the resinmaterial. It is noted that, if the wedge angle of the turning tool isset to 15 degrees or smaller, the life of the turning tool is shorten,although the cutting ability of the tool is improved. If the wedge angleof the turning tool is set to 35 degrees or larger, the cutting abilityof the tool is deteriorated, resulting in a high possibility ofoccurrence of defects, such as burrs, in the surface of the grooves. Theturning tool of the present invention has the wedged angle arrangedwithin a range of 15-35 degrees, thus making it possible to produce afine cutting into the polishing pad formed of the solid resin materialor the foamed rigid-resin material. Therefore, the turning tool of thepresent invention is capable of preventing occurrence of burrs on thesurface of the grooves, while assuring high processing accuracy. It isalso noted that if the front clearance angle of the turning tool is setto 45 degrees or smaller in the case where the cutting grooves haverelatively small radius of curvatures, the side surfaces of the cuttingpart of the turning tool is likely to interface with the radially outerwalls of the cutting grooves. This results in deterioration of adimensional accuracy of the grooves, due to occurrence of burrs,recesses and/or protrusions in the surface of the groove walls, anddulled open-end edges of the grooves. Further, the front clearance angleof 65 degrees or larger may adversely effect on the life of the cuttingparts of the turning tool.

[0021] According to a first preferred form of the turning tool of theinvention, the cutting part of the turning tool has a rake angle withina range of 20-10 degrees. It is noted that if the rake angle is set to20 degrees or larger, the cutting part of the turning tool is prone tocut undesirably into the inside of the polishing pad. On the other hand,if the rake angle is set to 10 degrees or smaller, the cutting abilityof the turning tool is deteriorated.

[0022] According to a second preferred form of the turning tool of theinvention, the cutting part has a side clearance angle with respect to aradially outer wall of each of said grooves, which is held within arange of 0-3 degrees. This arrangement enables to prevent or avoidinterface between the radially outer wall of each groove and the cuttingpart of the turning tool with high stability, thus making it possible toform the grooves with high dimensional accuracy of its radially outerwall portion, even if a radius of curvature of the groove is relativelysmall. An actual values of the side clearance angle may be suitablydetermined within the above-indicated range, taking into account ahardness or other specific physical properties of the work piece, i.e.,the polishing pad made of the resin material, and the value of the frontclearance angle of the tool, so that the cutting part of the turningtool is less likely to interface or cut into the radially outer wall ofthe each groove. If the side clearance angle exceeds 3 degrees,durability or proccessability of the cutting part of the tool may bedeteriorated, so that the side clearance is preferably set to 2 degreesor smaller. On the other hand, the side clearance angle of the cuttingpart with respect to a radially inner wall of each of the grooves can beset at around 0 degrees, since an interfere between the cutting part ofthe turning tool and the radially inner wall of the each groove is lesslikely to occur.

[0023] According to a third preferred form of the turning tool of theinvention, the turning tool includes a plurality of cutting parts whichare arranged in a predetermined direction with a pitch within a range of0.2-2.0 mm. The turning tool according to this preferred form makes itpossible to cut a plurality of generally concentric grooves with a widthwithin a range of 0.005-1.0 mm and with a radial pitch of 0.2-2.0 mmwith high efficiency. Preferably, the cutting parts are arranged in apredetermined direction with a generally constant pitch. According tothe actual experiment conducted by the inventor of the presentinvention, a tool having a single cutting part according to the presentinvention needs one hour or more for cutting an optional number ofgenerally concentric annular grooves into an optional base for thepolishing pad, while a multi edged tool having a plurality of cuttingparts constructed according to this preferred form of the turning toolof the invention can do the same work in minuets. It should beappreciated that such a multi-edged tool may be provided by utilizing atoll tip or a plurality of tool tips each having a plurality of cuttingparts integrally formed thereon, or alternatively by utilizing aplurality of cutting-part chips each having a single cutting part, whichare fixed together. Specific preferred form of the multi-edged tool willbe described hereinafter.

[0024] A first advantageous form of the multi-edged tool includes aplate-like shaped tool tip having a plurality of cutting partsintegrally formed at one of edge portions thereof so as to protrudeoutwardly from the one of the edge portions. Preferably, a plurality ofthe tool tips are fixedly arranged with each other so as to align in awidth direction thereof so that the cutting parts of the tool tipscooperate to form a multiplicity of cutting parts. Yet preferably, theturning tool of the invention further comprises a predetermined tool-tipholder to which the plurality of the plate-like shaped tool tips aredetachably fixed, so that the tool-tip holder and the plurality of tooltips cooperate to constitute a tool unit.

[0025] A second advantageous form of the multi-edged tool includes aplurality of cutting tips each having one cutting part, and theplurality of cutting tips are detachably fixed to each other so thatcutting parts of the plurality of cutting tips cooperate to form aplurality of cutting parts. Preferably, the plurality of cutting tipsare superposed on and integrally fixed to one another with spacersinterposed adjacent ones of the cutting tips so that the spacersfunction to keep a pitch of the plurality of cutting tips. Preferably,the turning tool of the invention further comprises a cutting-tip holderto which the plurality of cutting tips are detachably fixed, so that thecutting-tip holder and the cutting tips cooperate to constitute a unittool.

[0026] According to a fourth preferred form of the turning tool of theinvention, the cutting part has a tip portion arcuately curved in awidth direction thereof so that the tip portion has two end partsopposed in the width direction, wherein the two end parts of the tipportion protrudes outwardly from an intermediate part of the tip portionin a direction perpendicular to the width direction.

[0027] In the turning tool according to the fourth preferred form, thetwo end parts of the tip portion of the cutting part are initiallybrought into contact with the polishing pad as the working piece, upon astart of the cutting process. This arrangement permits an excellent andsmooth engagement of the cutting part of the turning tool with thesurface of the polishing pad, even in the case where the polishing padis formed of a constrictive member, e.g., a solid resin member and afoamed rigid-resin member, thus preventing undesirable dulling of theedge in the open end portion of the formed groove, in other words,undesirable increase of the width of the groove at the open end portionof the groove. Therefore, a polishing pad having grooves formed by usingthe cutting tool according to this preferred form of the first aspect ofthe invention, is capable of ensuring a desirable distribution ofslurry, and does not suffer from undesirable distribution of the slurrydue to the presence of the dulled edges in the open-end edge portions ofthe grooves. Further, the smooth engagement of the cutting part of theturning tool of this preferred from effectively prevent that a localportion of the polishing pad is excessively compressed by the cuttingpart of the cutting tool which is forcedly pressed thereon, in anattempt to ensure the engagement of the cutting part with the surface ofthe polishing pad, and is then damaged at a limiting point.

[0028] According to a fifth preferred form of the turning tool of theinvention, the cutting part has a tip portion being serrated. Like thearcuately curved cutting part as described above, the cutting part ofthis preferred form permits an excellent and smooth engagement thereofwith the surface of the polishing pad. In the turning tool of thispreferred form, it is desirable that a face, a front clearance face anda tooth surface may be provided with a fine polishing traces extendingin one direction e.g., a turning direction, or may be polished extremelysmoothly, for thereby facilitating flows of the cutting chips alongthese surfaces. Preferably, the side surfaces of the cutting part ofthis turning tool may be serrated.

[0029] The above-indicated second object of the invention may beachieved according to a second aspect of the invention, which provides amethod of producing a polishing pad made of a resin material, comprisingthe steps of: (a) positioning a turning tool constructed according tothe first aspect of the invention, relative to a base for the polishingpad made of the resin material; (b) rotating the cutting part of theturning tool and the base for the polishing pad relative to each otherabout an axis of the base for the polishing pad, so as to cutcircumferential grooves into a surface of the base, such that radiallyinner most one of the circumferential grooves has a radius of curvatureof 10 mm or smaller.

[0030] This method of the present invention makes it possible to form byturning fine circumferential grooves having a relatively small widthinto the base for the polishing pad made of a specific material such asa solid resin material or a foamed rigid-resin material, with highdimensional accuracy and ease. Moreover, the present method enables toform such fine accurate grooves in a very radially inner portion of thebase for the polishing pad.

[0031] According to a first preferred form of the method of the presentinvention, the turning tool is selected from the group of consisting ofthe turning tools of the above-described third preferred form of thefirst aspect of the invention, the first advantageous form of the thirdpreferred form of the first aspect of the invention, and the secondadvantageous form of the third preferred form of the first aspect of theinvention, and the circumferential grooves comprises a multiplicity ofgenerally concentric annular grooves, wherein the method furthercomprises the steps of: (c) simultaneously cutting the multiplicity ofgenerally concentric annular grooves into the surface of the base of thepolishing pad such that the radially inner most one of said multiplicityof generally concentric annular grooves has a radius of curvature of 10mm or smaller.

[0032] In this preferred form of the method of the invention, the use ofthe specific multi-edged turning tools constructed according to thepresent invention enables to form the multiplicity of fine generallyconcentric annular grooves into the surface of the base for thepolishing pad with an accurate dimensioned pitch and with highprocessing efficiency.

[0033] According to a second preferred form of the method of theinvention, the turning tool is adapted to cut the circumferentialgrooves into the surface of the base for the polishing pad at a feed perrevolution of 0.005-0.05 mm/rev in a depth direction of the base. Thisarrangement establish an excellent turning condition for cutting thegrooves by the present turning tool into the base for the polishing padwhich is made of a resin material in a solid state or a foamed state,e.g., a foamed urethane pad. Since the cutting of the grooves isperformed at the above-indicated slight feed per revolution, it ispossible to sequentially cut the surface of the base for the polishingpad without pressing the surface of the base for the polishing pad.Further, this method permits a smooth cutting of the finecircumferential grooves into the base for the polishing pad with highstability, without any defects such as undesirable cutting of theturning tool into the base and occurrence of burrs in the surface of theformed grooves. Preferably, the cutting parts and the base are rotatedrelative to each other at a speed of 50-300 rev/min. It is noted thatthe speed in the turning or cutting method according to the presentinvention may be desirably determined, taking into account physicalproperties of the base, quality of the cutting part and/or radius ofcurvatures of grooves to be formed.

[0034] According to a third preferred form of the method of theinvention, the method further includes the step of blowing ionic fluidtoward a vicinity of the cutting parts to neutralize the base for thepolishing pad and chips which are electrically charged due to executionof the step of cutting by the turning tool the circumferential groovesinto the surface of the base for the polishing pad.

[0035] Upon cutting the base for the polishing pad made of the resinmaterial by the present turning tool, the base and the tool are broughtin frictional contact with each other, thus generating staticelectricity having higher voltage. This may cause that the chips areelectrically charged and tend to adhere to the surface of the base andcutting part or parts of the turning tool. To eliminate this drawback,the ionic fluid is blown to the vicinity of the cutting part(s), thusneutralizing the electrically charged chips. This arrangement iseffective to avoid undesirable damages of the surface of the grooves dueto the presence of the cutting chips adhered to the surface of thegrooves or cutting parts of the tool. The blowing of the ionic fluid maybe executed continuously or discontinuously, or may be executed asneeded. Preferably, the ionic fluid is blown together with thecompressed air, so that the charged chips are neutralized and blown awayfrom the surface of the base for the polishing pad, simultaneously.

[0036] The above-indicated third object of the invention may be achievedaccording to a third aspect of the invention, which provides a polishingpad, which is effectively formed by using the turning tool constructedaccording to a first aspect of the invention, the polishing padcomprising: (a) a base made of a resin material; and (b) circumferentialgrooves open in a surface of the base, wherein the grooves have a widthwithin a range of 0.005-1.0 mm, a depth of 0.2-2.0 mm, and a pitch of0.2-2.0 mm, and wherein radially inner most one of the circumferentialgrooves has a radius of curvature of not larger than 10 mm.

[0037] In the polishing pad constructed according to the presentinvention, the circumferential grooves have a relatively small width anda sufficiently small pitch, in comparison with the known polishing padsas disclosed in the above-indicated U.S. Pat. Publication Nos. U.S. Pat.No. 5,921,855 and U.S. Pat. No. 5,984,769. This specific structure ofthe polishing pad of the present invention, which is distinguishablefrom that of the conventional polishing pads, enables that the surfaceof the polishing pad is deformed along a surface of a semiconductordevice, e.g., a wafer with improved accuracy, thus ensuring an excellentsurface polishing with high accuracy. Described more specifically, theconventional polishing pad requires an elastic backside pad fixed to thebackside of a base for the conventional polishing pad so as to absorb orcompensate a relatively large local deformation in the front surface ofthe base caused by bending of grooved portions of the base. Namely, thewall thickness of the base for the conventional polishing pad isdecreased at the grooved portion. Since the grooves have a relativelylarge width, the grooved portion is likely to bent, resulting in thelarge local deformation of the front surface of the base. Therefore, theconventional polishing pad needs the elastic backside pad to be deformedalong the surface of the wafer with desired accuracy. On the other hand,the polishing pad according to the present invention is effectivelyarranged to sufficiently decrease a width of partitions interposedbetween adjacent ones of the grooves and a width of each groove, therebyminimizing an amount of local deformation in the surface of thepolishing pad due to bending of the grooved portions, while allowingelastic deformation of the partitions so as to expand toward therespective grooves disposed opposite sides of the partitions (i.e.,expand in its radially opposite directions). This makes it possible thatthe surface of the polishing pad is deformed along the surface of thewafer with high accuracy, owing to the elastic deformations of thepartitions, thus ensuring a significantly high accurate polishing of thesemiconductor devices, that is never achieved by the conventionalpolishing pad. The polishing pad of the present invention is capable ofsuitably polishing semiconductor devices having interconnects made ofsoft metallic materials and arranged with a slight spacing therebetween.For instance, the polishing pad of the present invention enables for thefirst time to polish and planarize a substrate having multilevelinterconnections whose interconnect line has a width of 0.18 μm, 0.15 μmand/or 0.1 μm, with a high planarity level of 0.25 μm or lower.

[0038] Further, the polishing pad constructed according to the presentinvention can eliminate the need for the backside pad that isessentially required in the conventional polishing pad, making itpossible to simplify the structure of the polishing pad and tomanufacture the polishing pad with high efficiency. Therefore, thepolishing pad can be directly fixed to a platen of a polishing devicefor polishing semiconductor devices, without needing an elastic layer,such as the elastic backside pad interposed therebetween. This isbecause the present polishing pad permits an accurate surfacedeformation along the surface of the wafer on the basis of the elasticdeformation of the partitions, whereas the conventional polishing padutilizes an elastic backside pad to cause its surface to be deformedalong the surface of the wafer.

[0039] Preferably, the width of the each groove is arranged within arange of 0.1-0.3 μm so that the polishing pad can be deformed along thesurface of the wafer with further improved accuracy, owing to theelastic deformation of the partitions interposed between adjacent onesof the grooves. More preferably, the depth of the each grooves isarranged within a range of 0.1-0.4 μm, thereby improving durability ofthe polishing pad and minimizing an amount of change of properties ofthe polishing pad due to a dressing process or the like.

[0040] As is understood from the aforementioned description, the presentpolishing pad is different from the conventional polishing pad in themechanism for ensuring the desired surface deformation of the polishingpad along with the surface of the wafer. This distinguishablyadvantageous structure of the present invention permits that thepolishing pad and the surface of the wafer to be polished are pressedagainst with each other with a reduced pressing force, thereby furtherfacilitating flows of the slurry interposed between the polishing padand the surface of the wafer, and assuring substantially evendistribution of the pressing force over an entire area of the surface ofthe wafer to be polished. Accordingly, the polishing pad constructedaccording to the present invention permits an excellent polishing andplanarization of the surface of the semiconductor devices with extremelyhigh accuracy.

[0041] Preferably, the circumferential grooves comprises a multiplicityof generally concentric annular grooves which are formed over asufficiently large area of the front surface of the polishing padincluding a very radially inner portion. Namely, the radially inner mostgroove of the polishing pad has the radius of curvature of 1.0 mm orsmaller. This arrangement makes it possible to effectively increase aregion of the polishing pad serving for polishing, without increasingthe diameter of the polishing pad. This arrangement is also effective tokeep pace with recent tendency of enlargement of wafer, with ease. Itshould be appreciated that the use of the turning tool constructedaccording to the first aspect of the invention enables to form such anannular groove having a relatively small radius of curvature.

[0042] It is noted that if the groove width is smaller than 0.005 mm, itbecomes difficult to form such a fine groove by turning and to controlthe distribution of the slurry desirably. If the groove width is largerthan 1 mm, the polishing pad is likely to be excessively bent at itsgrooved portions, resulting in deterioration of polishing accuracy.Preferably, the groove width is set within a range of 0.1-1.0 mm.Further, if the generally concentric grooves are formed with a pitch ofsmaller than 0.2 mm, the polishing pad is likely to suffer from ahydroplane phenomenon depending upon a viscosity of the slurry. If thegenerally concentric grooves are formed with a pitch of larger than 2.0mm, the polishing pad is less likely to deform accurately along with thesurface of the wafer, resulting in deterioration of polishing accuracy.The pitch of the grooves may be desirably determined, taking intoaccount a required polishing accuracy, a kind of material ofinterconnects of the semiconductor device, or the like. Generally, thepitch of the grooves is determined within a range of 1.0-2.0 mm.

[0043] Preferably, the radially outer most one of the grooves has aradius of curvature of not less than 100 mm.

[0044] Yet preferably, the radially inner most one of the grooves has aradius of curvature of not larger than 10 mm, and the polishing pad hasa diameter which is made smaller than that of the working piece. Thispolishing pad constructed according to this preferred form iseffectively used for polishing a significantly large sized wafer, e.g.,a wafer having a diameter of not smaller than 200 mm. Since the radiallyinner useless area of the polishing pad is effectively minimized, thepolishing pad of this preferred form makes it possible to polish such alarge-sized wafer without increasing a diameter thereof.

[0045] It may be possible to vary the pitch of the grooves in the radialdirection of the polishing pad. For instance, the grooved portion of thesurface of the polishing pad may be divided into three regions, namely,an inner circumferential region, an intermediate region, and an outercircumferential region. The pitch of the grooves may desirably varyamong the three regions so that the polishing pad may polish evenly thesurface of the semiconductor device.

[0046] It may also be possible that the circumferential grooves arespaced apart from each other in the radial direction of the polishingpad with a constant pitch. This arrangement facilitates a manufacture ofthe polishing pad, and stabilizes a desirable deformation of the surfaceof the polishing pad following the surface of the wafer on the basis ofthe elastic deformation of the partitions interposed between adjacentones of the grooves.

[0047] According to another preferred form of the polishing pad of thepresent invention, the base for the polishing pad is made of a rigidurethane foam and the circumferential grooves are formed with a width of0.20-0.30 mm, a depth of 0.1-1.0 mm, more preferably 0.1-0.4 mm and apitch of 1.0-2.0 mm. In this form of the polishing pad, kinds of therigid urethane foam are not particularly limited. Preferably, the baseis formed of a rigid urethane foam having a density at around 700 kg/m³and a tensile strength of 50 kg/cm³ or more. More preferably, therigid-urethane foam includes cells having a diameter at around 0.02 mmat the volume ratio of 30%. In this respect, a rigid urethane foam usedas packing material, generally has a density at around 100 kg/m³ and atensile strength at around 15 kg/cm³. It should be appreciated that asolid resin member may also form the base.

[0048] The above-indicated fourth object of the invention may beachieved according to a fourth aspect of the invention, which provides amachine equipped with a turning tool constructed according to the firstaspect of the invention and adapted to form a polishing pad constructedaccording to a third aspect of the present invention. The machine forgrooving a base for a polishing pad made of a resin material, comprises(a) a bed; (b) a platen including a hollow shaft member supported by thebed via bearing so that the hollow shaft member is rotatably about aC-axis which is perpendicular to the bed, a suction plate fixed to oneof opposite axial end portion of the hollow shaft member remote from thebed and formed with a plurality of through holes arranged evenly over anentire area thereof for attracting the base for the polishing pad to beplaced on the suction plate; (c) drive mechanism for rotating the platenabout the C-axis and for positioning the platen at a suitable angularposition; (e) a gate-shaped column having two legs which are opposed toeach other with a spacing therebetween and a cross rail extendingbetween and being perpendicular to the two legs, the gate-shaped columnbeing movable in a direction of X-axis with the cross rail extendingacross the platen; (f) at least one saddle mounted on the cross rail soas to be movable in a direction of Y-axis extending along with the crossrail; (g) a tool rest mounted on the saddle so as to be independentlyreciprocally movable in a direction of a Z-axis, the tool rest adaptedto detachably hold a fixed tool comprising the turning tool constructedaccording to the first aspect of the invention; (h) drive motors formoving and positioning the platen, the column and the saddle and thetool rest; and (i) a numerical control apparatus totally control anoperation of the drive motor, wherein the hollow shaft member of theplaten is connectable to an external air suction device so as to attractthe base for the polishing pad on the suction plate by a suction forceapplied from said air suction device to said base for said polishingpad, and wherein the machine is operable to cut by the turning toolcircumferential grooves into a surface of the base of the polishing padwith the base for the polishing pad being attracted on the suctionplate.

[0049] The machine constructed according to the fourth object of thepresent invention, makes it possible to form by turning thecircumferential grooves on the surface of the base for a thin polishingpad, which is made of a resin material in a solid state or a foamedstate, e.g., a rigid urethane foam, by using a specific turning toolconstructed according to the first aspect of the present invention. Thecircumferential grooves can be formed with high accuracy and highstability over a substantially entire area of the surface of the basefor the polishing pad. Therefore, the machine is able to effectivelyform the polishing pad constructed according to the third aspect of thepresent invention.

[0050] In this respect, there are known various kinds of conventionalgeneral-purpose turning machines, such as lathes and machining centers.These known turning machines are provided for mainly processing ametallic work piece, and are equipped with a rotative platen adapted tofix the metallic working piece thereon by holding a periphery of thework piece, a tool rest holding a cutter (fixed tool), a drive mechanismfor positioning the cutter relative to the working piece and forrotating the cutter and the work piece relative to each other, and acontroller for controlling operation of the driving mechanism, forexample. That is, the known turning machines may possibly be operable tocut the circumferential grooves with a desired pitch into a work piecefixed to the rotative platen. However, since the base for the polishingpad as the work piece is made of the resin material and has a relativelysmall thickness, it is therefore difficult to stably fix such a specialworking piece, i.e., the base for the polishing pad on the platen byonly holding the peripheral portion of the base. For the above reasons,the conventional turning machine is incapable of controlling a depth ofcut of the turning tool by a slight amount, which is required forcutting the desired circumferential grooves into the surface of the basefor the polishing pad. Thus, the conventional turning machine is neverutilized for forming the polishing pad constructed according to thethird aspect of the present invention.

[0051] Moreover, the polishing pad to be processed by the machine of thepresent invention has a large variety of required properties, needing achange of the turning tool depending upon properties of the desiredpolishing pad. However, the conventional turning machine suffers from asmall degree of freedom in choosing turning tools, and accordingly isnot able to meet such requirements in the grooving process of thepolishing pad.

[0052] In addition, the conventional turning machine has an excessivelylarge rigidity for processing the base for the polishing pad, thusmaking the grooving process complicated and time-consummative. Namely,in the conventional turning machine, each of the moving components has arelatively large mass and a resultant large inertia, making it difficultto ensure a faster operation of the components of the machine.

[0053] In the grooving machine for producing the polishing pad accordingto the present invention, the base for the polishing pad as the workpiece is suctioned on and firmly fixed to the circular platen. Thisarrangement eliminates or reduces a possible distortion of the basegenerated upon rotating the circular platen. Further, the circularplaten is arranged to substantially evenly apply the suction force overan entire area of a rear surface of the base for the polishing pad,making it possible to form by turning the groves into the surface of thebase with improved processing accuracy and high stability.

[0054] In the grooving machine of the present invention, the gate-shapedcolumn is disposed on the bed with the circular platen interposedbetween its legs, while a saddle is formed on the cross rail of thegate-shaped column adapted to support tools. This arrangement ensures ahigh stable and accurate positioning of the tools relative to theworking pieces in comparison with the case where the tools are supportedby a single arm, while assuring an increased working area of the tools.

[0055] According to a first preferred form of the machine of theinvention, the machine further comprises: (j) an ion blowing device forneutralizing the static electricity charged in the polishing pad andchips, for separating the chips from the fixed tool and the polishingpad, said ion blowing device including: an ion generating device forgenerating ion, an ion extruding nozzle for extruding the ion toward thecutting part of the fixed tool, an air blowing device for blowing airtogether with the ion.

[0056] According to a second preferred form of the machine of theinvention, the tool rest detachably support a rotative tool consistingof a milling cutter unit and/or a drilling unit. In this preferred formof the machine of the present invention, the tool rest is adapted toselectively support a milling cutter unit including a milling cutter forgrooving and a drill unit having a drilling cutter, as well as theturning tool for grooving constructed according to the first aspect ofthe invention. Therefore, the machine of this preferred form is operableto execute not only the grooving process but also milling cutting anddrilling processes.

[0057] In one advantageous form of the second preferred form of themachine of the invention, the milling cutter unit includes at least onemilling cutter fixedly supported by a tool shaft extending along acenter axis thereof, wherein the at least one cutter includes adisk-shaped body member and a plurality of cutting edges disposed at anouter peripheral portion of said body member at regular angularintervals, and each having a wedge angle within a range of 20-40degrees, and a front clearance angle within a range of 30-40 degrees, atooth width within a range of 0.3-2.0 mm, and a side cutting edge angleof 0-2 degree. The use of the milling cutter having a specialconstruction as described above enables the machine to process the basefor the polishing pad with increased degree of freedom. For instance,the use of this special milling cutter permits the present machine toform with ease grooves arranged in a grid pattern, a spiral pattern, aspoke-wise pattern and other formable patterns.

[0058] Preferably, the machine comprises a plurality of the millingcutters which are fixedly disposed onto the tool shaft such that thetool shaft extend through center axes of the plurality of the millingcutters and the plurality of milling cutters are spaced apart from eachother in an axial direction of the tool shaft with a uniform pitch of0.1 mm or more. This arrangement makes it possible to cut a plurality ofgrooves into the surface of the base for the polishing pad,simultaneously.

[0059] In another advantageous form of the second preferred form of themachine of the invention, the drill unit comprises a single-spindle typeor a multiple-spindle type drill unit, the drill unit including a drillhaving a drill diameter of 0.5-1.5 mm, a drill length of 20-30 mm twocutting edges of helix angle of 1-10 degrees, wherein the drill is astraight drill having no back-tapered portion at cutting edges thereofand having a shape edge that has a conical angle with no chisel portionof 55-65 degrees. The use of this drilling unit permits the presentmachine to cut holes into or through the base for the polishing pad,resulting in an increased degree of freedom in processing the base forthe polishing pad. In particular, the drill of the drilling unit isspecifically arranged as described above, in other words, the drill hasthe sharp edge in the conical shape so as to facilitate entrance of thedrill into the base, and the cutting edges arranged at its body portionwith a relatively dull helical angle so as to perform cutting of thebase with a slight amount of feed per revolution. This arrangementminimizes a possibility that the end of the drill damages the base.Thus, the machine equipped with the drilling unit can form a hole at adesired diameter with high accuracy.

[0060] According to a third preferred form of the machine of theinvention, the machine further comprises a sequential control systemadapted to control operation of the drive motor in place of or inaddition to the numerical control apparatus. The use of the sequentialcontrol system may slightly restrict operation speed and commandaccuracy in comparison with the numerical control apparatus. However,the use of the sequential control system may sometimes be advantageousin terms of cost depending upon kinds of applications, thus extending afield of application of the present machine.

[0061] According to a fourth preferred form of the machine of theinvention, the machine includes two of the saddles, wherein at least oneof the tool holders of the two saddles is adapted to detachably supportthe fixed tool comprising the turning tool comprising a cutting partarranged to have a tooth width within a range of 0.005-1.0 mm, a wedgeangle within a range of 15-35 degrees, and a front clearance anglewithin a range of 65-45 degrees, and an other one of the tool holders ofthe two saddles is adapted to detachably support the rotative toolselected from a group consisting of the milling cutter unit and thedrilling unit. In this arrangement the machine is equipped with both ofthe turning tool and the rotative tool with high efficiency, whereby themachine is able to execute various kinds of processing with improvedoperation efficiency.

[0062] According to a fifth preferred form of the machine of theinvention, the machine includes only one of the saddle, wherein the toolholder of the saddle is adapted to interchangeably support the fixedtool comprising the turning tool constructed according to the firstaspect of the invention or the rotative tool selected from a groupconsisting of the milling cutter unit or the drilling unit. In thisarrangement, the grooving machine is made compact in size and simple inconstruction, while enabling selective use of the fixed tool and therotative tool.

BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The forgoing and/or other objects features and advantages of theinvention will become more apparent from the following description ofpreferred embodiments with reference to the accompanying drawings, inwhich like numerals are used to represent like elements and wherein:

[0064]FIG. 1A is an front elevational view of a grooving machineconstructed according to one preferred embodiment of the presentinvention, and FIG. 1B is an plane view of the grooving machine of FIG.1A, while FIG. 1C is a side elevational view of the grooving machine ofFIG. 1A;

[0065]FIG. 2 is an elevational view in a vertical or a longitudinalcross section of the grooving machine of FIG. 1A;

[0066]FIG. 3 is an fragmentally enlarged view of the grooving machine ofFIG. 1A;

[0067]FIG. 4A is a plane view of a platen of the grooving machine ofFIG. 1, and FIG. 4B is a cross sectional view of the platen of FIG. 4Ataken along line B-B of FIG. 4A;

[0068]FIG. 5A is a plane view of a suction plate of the grooving machineof FIG. 1, FIG. 5B is an axial cross sectional view of the suctionplate, FIG. 5C is a fragmentally enlarged view of the suction plate,FIG. 5D is an enlarged view of a X portion of FIG. 5C, and FIG. 5E is anenlarged cross sectional view taken along line E-E of FIG. 5D;

[0069]FIGS. 6A and 6B are a front and a side views of the groovingmachine of FIG. 1A, which are depicted for explaining a primary part ofthe grooving machine of FIG. 1A;

[0070]FIGS. 7A and 7B are a plane and a rear view of the groovingmachine of FIG. 1A, which are depicted for explaining a primary part ofthe grooving machine of FIG. 1A;

[0071]FIGS. 8A and 8B are a front and a cross sectional views of saddlesof the grooving machine of FIG. 1, which are depicted for explaining adrive system of the saddles movable along a Y1 axis and a Y2 axis,respectively;

[0072]FIGS. 9A and 9B are a front and a side elevational view of aninside of the grooving machine of FIG. 1A, which are depicted forexplaining a drive system of the tool holders movable along a Z1 axisand a Z2 axis, respectively;

[0073]FIG. 10 is a fragmentally side elevational view of the groovingmachine of FIG. 1A, which shows one operating state of the groovingmachine in which a milling tool is attached to the tool holder;

[0074]FIG. 11 is a view corresponding to FIG. 10, which shows anotheroperating state of the grooving machine in which a drill tool isattached to the tool holder;

[0075]FIG. 12 is a view corresponding to FIG. 10, which shows yetanother operating state of the grooving machine in which a fixed tool isattached to the tool holder;

[0076]FIG. 13 is a block diagram schematically illustrating an essentialstructure of a numerical control device employed for controllingoperation of the grooving machine of FIG. 1A;

[0077]FIG. 14 is a block diagram schematically illustrating an essentialstructure of a sequence control device employed for controllingoperation of the grooving machine of FIG. 1A;

[0078]FIG. 15A is a front elevational view of an ion blowing device usedin the grooving machine of FIG. 1 for neutralizing charged components ofthe grooving machine, and FIGS. 15B and 15C are a side and a bottomelevational view of the ion blowing device, respectively;

[0079]FIGS. 16A and 16B are a front and a side views of a turning toolhaving a single cutting part, which is usable in the grooving machine ofFIG. 1;

[0080]FIGS. 17A and 17B are a side and a front view of a turning toolhaving a plurality of cutting parts, which is usable in the groovingmachine of FIG. 1;

[0081]FIG. 18 is an enlarged front elevational view of one example of atool tip;

[0082]FIGS. 19A and 19B are a front and a side view of a tool holder towhich the tool chip of FIG. 18 is attached;

[0083]FIG. 20 is an explanatory view showing one example of operationstate of the grooving machine of FIG. 1, in which a plurality of toolchips attached to the tool holder are arranged in one direction;

[0084]FIG. 21 is an explanatory view showing one example of operationstate of the grooving machine of FIG. 1, in which a plurality of toolchips of FIG. 18 are fixed to the tool holder;

[0085]FIG. 22A is an enlarged side view of one example of a multi-edgedtool tip in which a plurality of cutting parts are laminated oneanother, and FIG. 22B is an enlarged front elevational view of themulti-edged tool of FIG. 22A;

[0086]FIG. 23A is an enlarged side view of another example of amulti-edged tool tip in which a plurality of cutting edges are laminatedone another, and FIG. 23B is an enlarged front elevational view of thetool tip of FIG. 23A;

[0087]FIG. 24A is a side view of one example of a cutting device usablein the grooving machine of FIG. 1, FIG. 24B is a front elevational viewof the cutting device, and FIG. 24C is a cross sectional view of thecutting device, taken along line C-C of FIG. 24B;

[0088]FIG. 25A is a plane view of one example of a milling cutterattachable to the milling tool of FIG. 10, and FIG. 25B is afragmentally enlarged view of the milling cutter of FIG. 25A;

[0089]FIG. 26A is a plane view of one example of a drill attached to adrill unit of FIG. 11, and FIG. 26B is an exploded view of a majorcutting edge portion of the drill of FIG. 26A;

[0090]FIGS. 27A and 27B show one example of a polishing pad of foamedurethane having a plurality of generally concentric grooves formed bycutting process executed by the grooving machine of FIG. 1, wherein FIG.27A is a fragmentally enlarged plane view of the polishing pad, and FIG.27B is a fragmentally enlarged view in cross section of the polishingpad;

[0091]FIGS. 28A and 28B show another example of polishing pad of foamedurethane having a plurality of grooves arranged at grid pattern formedby milling process executed by the grooving machine of FIG. 1, whereinFIG. 28A is a fragmentally enlarged plane view of the polishing pad, andFIG. 28B is a fragmentally enlarged view in cross section of thepolishing pad;

[0092]FIG. 29 is yet another example of polishing pad of foamed urethanehaving a plurality of grooves arranged in a radial pattern formed bymilling process executed by the grooving machine of FIG. 1;

[0093]FIG. 30 is still another example of polishing pad of foamedurethane according to examples 1 and 2 by using the grooving machine ofFIG. 1 equipped with the turning tool of FIG. 17;

[0094]FIG. 31 is a fragmentally enlarged view in axial cross section ofthe polishing pad of FIG. 30;

[0095]FIG. 32A is a microscopic photographic view of 30 timesmagnification and FIG. 32B is a microscopic photographic view of 100times magnification, which shows a cross sectional shape of grooves ofone example of a polishing pad of the present invention, which groovesare formed by using the turning tool of the present invention;

[0096]FIG. 33A is a microscopic photographic view of 30 timesmagnification and FIG. 33B is a microscopic photographic view of 100times magnification, which shows a cross sectional shape of grooves of acomparative example of a polishing pad;

[0097]FIG. 34 is a microscopic photographic view of 120 timesmagnification showing a cross sectional shape of grooves of anotherexample of a polishing pad of the invention;

[0098]FIG. 35 is a microscopic photographic view of 120 timesmagnification showing a cross sectional shape of grooves of anothercomparative example of a polishing pad;

[0099]FIG. 36 is a microscopic photographic view showing grooves formedin a radially inner portion of a polishing pad of the present invention;

[0100]FIG. 37 is a view schematically showing a static model used in asimulation of relationship between a groove width variation and anabutting pressure variation of a polishing pad of the invention withrespect to a wafer;

[0101]FIG. 38 is a graph showing a distribution of an abutting pressureof the polishing pad on a surface of the wafer of the static model ofFIG. 37; and

[0102]FIG. 39 is a graph showing a relationship between a peak pressureapplied on the surface of the wafer and a rate of variation or error ofa groove width.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0103] Referring first to FIGS. 1A-1C, there is shown a schematicconstruction of a grooving machine according to one preferred embodimentof the present invention. The grooving machine is equipped with aturning tool for cutting grooves, which is constructed according to onepreferred embodiment of the invention. The grooving machine is used forproducing a polishing pad according to one preferred embodiment of theinvention in accordance with a method according to one preferredembodiment of the invention.

[0104] The grooving machine constructed according to the presentembodiment is operable to produce by cutting circumferential grooves,e.g., a multiplicity of generally concentric annular grooves in thepresent embodiment, on a surface of a base for the polishing pad made ofa resin material, e.g., a foamed urethane pad 15. The grooving machinecomprises the following components:

[0105] (a) a circular platen 1 rotatable under control about C-axisextending in a vertical direction as seen in FIG. 1A;

[0106] (b) a gate-shaped column 11 reciprocatory movable under controlin a direction of X-axis;

[0107] (c) two saddles 8A, 8B mounted on a cross rail 7 andreciprocatory movable along a screw-thread 10 (Y1-axis) and ascrew-thread 14 (Y2-axis);

[0108] (d) two tool holders 18, 19 mounted on the two saddles 8A, 8B;respectively, and reciprocatory movable along a screw-thread 12A(Z1-axis) and a screw-thread 12B (Z2-axis);

[0109] (e) a numerical control device 102 (see FIGS. 13, 14) adapted tocontrol operation of motor and a control axis;

[0110] (f) an ion blower 114 as an ion blowing device (see FIG. 15) forneutralizing charged components;

[0111] (g) a fixed tool 69 as a turning tool in the form of a singlecutting edge tool 58 and a multiple cutting edges tool 74 (see FIG. 12)for cutting grooves;

[0112] (h) a cutting device (see FIG. 24); and

[0113] (i) a rotative tool 57 in the form of a milling tool 59 and adrill unit 65 (see FIGS. 10, 11).

[0114] There will be described in detail a general construction of thegrooving machine and specific construction of the respective componentslisted above, with reference to the accompanying drawings, sequentially.

[0115] FIGS. 1A-1C shows an entire construction of the grooving machineaccording to the present embodiment. The circular platen 1 is fixedlymounted on a bed 3 so as to extend parallel to an upper surface of thebed 3. The circular platen 1 is rotatable about the C-axis extendingperpendicular to the upper surface of the bed 3, i.e., extending in thevertical direction as seen in FIG. 1A. The bed 3 further supports a pairof first guide rails 5A, 5B horizontally mounted on opposite sides ofits upper surface. The first guide rails 5A, 5B extend parallel to eachother in a longitudinal direction of the bed 3 while being spaced apartfrom each other with the circular platen 1 interposed therebetween. Thegate-shaped column 11 is mounted on the first guide rails 5A, 5B so thatthe gate-shaped column 11 is movable along the first guide rails 5A, 5Bin the horizontal direction. The gate-shaped column 11 includes a pairof legs in the form of column portions 4A, 4B mounted on the first guiderails 5A, 5B, respectively, and a cross rail 7 extending between thecolumn portions 4A, 4B so as to connect the column portions 4A, 4B toeach other. The thus formed gate-shaped column 11 is driven by a pair ofscrew shaft 6A (first X axis) and 6B (second X axis) disposed on the bed3 so as to extend along the guide rails 5A, 5B, respectively, in adirection of an X-axis as indicated by an arrow in FIG. 1B. The pair ofscrew shafts 6A, 6B are synchronously rotated by a drive motor 40 whichwill be described later with reference to FIG. 7B. The drive of thegate-shaped column 11 is controlled by a suitable control device thatwill be described later. A pair of second guide rails 9A, 9B aredisposed on one of opposite side faces of the cross rail 7 so as toextend in a direction of a Y-axis as indicated by an arrow in FIGS. 1Aand 1B, which is perpendicular to the X-axis. On the second guide rails9A, 9B, the two saddles 8A, 8B are mounted so as to be movable along theguide rails 9A, 9B, i.e., in the direction of the Y-axis. The twosaddles 8A, 8B are driven by respective screw shafts 10, 14 disposed onthe side face of the cross rail 7 so as to extend along the guide rails9A, 9B. The screw shafts 10, 14 are rotated by suitably electric drivemotors (not shown) under control of the suitable control device. The twosaddles 8A, 8B support tool rests 18, 19 mounted thereon, respectively,such that the tool rests 18, 19 are movable in a direction of a Z-axisextending in the vertical direction as seen in FIG. 1A (as indicated byan arrow). The tool rests 18, 19 are driven by respective ball-screws12A, 12B disposed on the saddles 8A, 8B so as to extend along theZ-axis. The screw shafts 12A, 12B are rotated by respective electricmotors 13A, 13B so that the tool rests 18, 19 are moved in the directionof the Z-axis independently of each other. The gate shaped column 11,the saddles 8A, 8B, and the tool rests 18, 19 may be formed by desiredmetallic materials, preferably rigid light metallic materials such as ahard aluminum alloy or the like.

[0116] (a) Circular Platen (C-Axis)

[0117] Referring next to FIG. 2, the circular platen 1 and a housingmember of the circular platen 1 are both shown in their axial crosssections. FIG. 2 also shows a driving mechanism for rotating thecircular platen 1 and an air suction device in the form of a suctionblower 25 installed within the bed 3 so as to apply a vacuum to an uppersurface of the circular platen 1 to thereby attract the base for adesired polishing pad for the CMP, in the form of the foamed urethanepad 15, on the upper surface of the circular platen 1. FIG. 3 shows anenlarged view in axial cross section of a position holding member 38adapted to place the circular platen at its suitable angular positionabout the C-axis, which is determined based on the angular position ofthe circular platen 1 detected by controlling the rotation of thecircular platen 1 about the C-axis. FIG. 4 shows a plane view and anaxial cross sectional view of the circular platen 1 in which a pluralityof air flow passages are evenly formed therethrough so that the vacuumdelivered from the suction blower 25 is evenly applied to a rear surfaceof the foamed urethane pad 15. FIG. 5 shows a suction plate 16 assembledin the surface of the circular platen 1. The suction plate 16 has aplurality of tiny air holes 16 a formed therethrough and tiny grooves 16b, 16 c connecting the air holes 16 a so that the vacuum is evenlyapplied to the rear surface of the foamed urethane pad 15, thuspreventing deformation of the surface of the urethane pad due to stressconcentrated at a local portion of the foamed urethane pad upon cuttinggrooves on the urethane pad.

[0118] As is understood from FIGS. 2 and 3, the circular platen 1 issupported by a hollow shaft member in the form of a hollow center shaft17 that is disposed in and supported by the bed 3 via the housing 2,such that the hollow center shaft 17 is rotatable about a center axisthereof. Described in detail, the center shaft 17 has an outward flangeportions 17 a integrally formed at an axially upper end portion thereof.The circular platen 1 is placed on and fixed to an annular upper surfaceof the outward flange portion 17 a so as to extend in a radial directionperpendicular to the center axis of the center shaft 17. The centershaft 17 is fixed at its axially upper and lower end portions to thehousing 2 via upper and lower bearings 33, 34, respectively. The type,size and level of dimensional accuracy of the upper and lower bearings33, 34 are suitably determined so that an amount of deflection occurredat an outer peripheral portion and the upper surface of the circularplaten 1 is significantly reduced. The housing 2 is fixed to the bed,whereby the center shaft 17 is rotatably supported by the bed 3.

[0119] The axially lower end portion of the center shaft 17 protrudesaxially downwardly from the housing 2. To the protruded end portion ofthe center shaft 17, an optional power transmittal member, e.g., apulley 22 is fixed. On the other hand, a drive motor 21 operable forcontrolling the rotation of the circular platen 1 about the C-axis isfixed to a sheet portion 3 a of the bed 3. The output power of the drivemotor 21 is transmitted via pulleys 22, 23 and a belt 24 rounded aboutthe pulleys 22, 23, thus generating a rotation of the center shaft 17and the circular platen 1 fixed to the center shaft 17 about the C-axis.In this respect, power transmitting mechanism for transmitting theoutput power of the drive motor 21 to the center shaft 17 may otherwisebe constituted by utilizing a combination of gears, or any otherpossible power transmittal members.

[0120] The hollow center shaft 17 has a bore 17 b serving as an airpassage. The bore 17 b is held in fluid-tight communication at its upperend with a plurality of communication holes 1 a formed through thecentral portion of the circular platen 1, and at its lower end with anair hose 28 of the suction blower 25 via a coupling 27 supported by asupport 26 fixed to a seat portion 3 b of the bed 3. In this condition,the vacuum generated in the suction blower 25 is applicable to the rearsurface of the foamed urethane pad placed on the upper surface of thecircular platen 1 through the bore 17 b of the center shaft 17 and thecommunication holes 1 a of the circular platen 1. Therefore, the vacuumapplication needed for holding the foamed urethane pad on the surface ofthe circular plate 1 can be executed during the rotation of the centershaft 17. In this respect, the upper open end of the communication holes1 a are closed by a suction plate 16 which is placed on the uppersurface of the circular platen 1. As shown in FIG. 5, the suction plate16 is formed with a plurality of suction holes in the form of air holes16 a and grooves 16 b, so that the vacuum is evenly applied in the uppersurface of the suction plate 16 through the communication holes 1 a andthe air holes 16 a and the grooves 16 b, thus assuring firmly holding ofthe foamed urethane pad 15 on the surface of the suction plate 16. As isunderstood from the aforementioned description, the position holdingmember 38, the drive motor 21 and the suitable power transmittal memberscooperates to form a drive mechanism adapted to rotate the circularplaten 1 and place the circular platen 1 at a suitable angular position,in the present embodiment.

[0121] Referring back to FIGS. 2 and 3, a disk plate 30 having aplurality of projections 31 is fixed to the protruding end portion ofthe center shaft 17, while plurality of sensors 32 are fixed to thelower end face of the housing 2 so as to be located above theprojections 31 with a slight spacing therebetween in the verticaldirection as seen in FIG. 2. The sensors 32 detect the projections 31 tothereby detect the angular position of the circular platen 1. Thismechanism is used for detecting the angular position of the circularplaten 1 rotating about the C-axis under control, and positioning thecircular platen 1 at its desired angular position. When the groovingmachine is operated to form a multiplicity of small-width straightgrooves arranged in a grid pattern on the surface of the foamed urethanepad 15, by using the milling cutter, the positions of the sensors 32 andthe projections 31 are changed so that the sensors 32 can detect angularpositions of the circular platen 1 each time the circular platen 1 isrotated by 45 degree about the C-axis. In the grooving process, thecircular platen 1 is fixed each time the circular platen is rotated by90 degree about the C-axis, to thereby cutting the straight grooves onthe surface of the urethane pad in the grid pattern. In the presentembodiment, the position holding member 38 is constituted by apositioning bush 35 having a tapered hole, which is fixed to apredetermined angular position of the lower surface of the circularplaten 1, and a piston member 37 having a shaft 36 whose upper endportion is tapered, which is disposed on a corresponding angularposition of the bed 3. The piston member 37 may be of pneumatic type,hydraulic type or alternatively electromagnetic type. It should beappreciated that the structure of the position holding member 38 is notparticular limited to the illustrated one. For instance, a Curviccoupling device (curvic: trademark) may be employed instead of thetapered shaft 36, for thereby permitting the detection of the angularposition of the circular platen 1 at angular intervals of not largerthan 45 degree.

[0122]FIG. 4A shows a plane view of the circular platen 1, while theFIG. 4B shows a cross sectional view of the circular platen 1 takenalong line B-B of FIG. 4A. A material for producing the circular platen1 may be preferably selected from light metals including aluminum alloy,titanium and the like, thereby lowing a moment of inertia of thecircular platen 1, thus permitting a prompt startup or stop of therotation of the circular platen. In particular, the material of thecircular platen 1 is desired to be less likely to cause the secularchange of the circular platen 1, like strain, to exhibit a heatresistance, and to have sufficient stiffness and strength. While thecommunication holes 1 a is formed through the central portion of thecircular platen 1 for introducing the suction force applied from thesuction blower 25 into the upper surface of the circular platen 1through, the circular platen 1 is also formed with a plurality ofleading grooves 1 c, 1 d for leading the suction force into the outercircumferential portion of the circular platen 1. The circular platen 1is further provided with a plurality of generally concentric grooves 1e, through which the plurality of leading grooves 1 c, 1 d extending inthe radial directions are held in communication with each other. Aplurality of circumferential walls 1 f defined between adjacent ones ofthe annular grooves 1 e serve as supports on which the suction plate 16is placed.

[0123] Referring next to FIGS. 5A, 5B, 5C, there are shown a plane view,an axial cross sectional view, and a fragmentally enlarged view of thesuction plate 16. In addition, FIG. 5D shows an enlarged view of an Xpart of FIG. 5C, and FIG. 5E shows a cross sectional view taken alongline E-E of FIG. 5D. As shown in FIG. 5E, the suction plate 16 functionsto support the foamed urethane pad 15 to be placed thereon. The suctionplate 16 is provided with the multiplicity of tiny air holes 16 a evenlydispersed over the entire surface of the suction plate 16, so that thefoamed urethane pad 15 is fixed onto the surface of the suction plate 16by the suction force evenly applied to the back surface thereof throughthe air holes 16 a. Like the circular platen 1, the suction plate 16 ismade of a material preferably selected from light metals including hardaluminum alloy, titanium, and the like, and ceramic materials.

[0124] In the light of flexibility of the foamed urethane pad 15,specific arrangement is needed for ensuring desired suction condition ofthe foamed urethane pad 15 on the suction plate 16. More specificallydescribed, when the currently processed portion on the front surface ofthe foamed urethane pad is remote from suctioned portions on the rearsurface of the foamed urethane pad 15 to which the suctioned force isapplied, the processed foamed urethane pad 15 is prone to be deformed ordisplaced in the direction in which the cutting tool is forwarded,possibly causing deterioration of dimensional accuracy of the formedgrooves. To cope with this problem, the suction plate 16 is required tobe capable of evenly applying the suction force on the rear surface ofthe foamed urethane pad 16 placed thereon. Therefore, the air hole 16 aare evenly dispersed over the entire area of the suction plate 16 with asubstantially regular pitch. Each of the air holes 16 a is dimensionedto have a suitable diameter, taken into account the thickness of thefoamed urethane pad 16, so that the suction force applied through theair hole 16 a to the corresponding portion of the rear surface of theurethane pad 16 does not cause deformation of the urethane pad 16. Forinstance, the air hole 16 a is dimensioned to have a diameter of about 2mm, when the foamed urethane pad 15 has a thickness of 1.4 mm. As shownin FIG. 5D, adjacent ones of the air holes 16 a are held incommunication with each other through communication grooves 16 b, thusassuring further improved evenness of the suction force. The suctionplate 16 is further provided with a plurality of annular generallyconcentric clearance grooves 16 c, which are formed on predeterminedradial portion of the front surface of the suction plate 16. In the casewhere the grooving machine is operated to perform a boring process witha boring unit in the form of a drill unit 65 (which will be describedlater with reference to FIGS. 11 and 16 ) attached thereto, the suctionplate 16 is further provided with a clearance grooves (not shown) havinga diameter slightly larger than the diameter of a drill of the drillunit 65 and formed through its predetermined portion.

[0125] (b) Gate-Shaped Column (X-Axis)

[0126] Referring next to FIGS. 6A and 6B, there are shown a plane viewand a side view of the gate-shaped column 11 that is placed on the firstguide rails 5A, 5B, which are disposed on the bed 3 with the circularplaten 1 interposed therebetween. FIGS. 7A and 7B show drive mechanismfor driving the gate-shaped column 11 in the direction of the X-axis asshown in FIG. 7A. Namely, FIG. 7A is a plane view of the bed 3 on whichthe pair of screw shafts 6A, 6B are disposed so as to extend along withthe guide rails 5A, 5B, respectively. The motions of the screw shafts6A, 6B in their axial direction i.e., in the direction of X-axis, arecontrollable. FIG. 7B shows a power transmitting system for controllingthe rotation of the screw shaft 6A, 6B by using a single belt 43.

[0127] Described more specifically, the gate-shaped column 11 includesthe pair of columns 4A, 4B and the cross rail 7 fixed at its both endswith the columns 4A, 4B, respectively, for thereby connecting thecolumns 4A, 4B. The pair of columns 4A, 4B are placed on the first guiderails 5A, 5B, respectively, so that the gate-shaped column 11 is movablein the direction of an X axis along the guide rails 5A, 5B, by the driveforce generated by the screw shafts 6A, 6B. Alternatively, thegate-shaped column 11 may be formed as an integral form by welding orcasting.

[0128] As shown in FIGS. 7A, 7B, the first pair of screw shaft 6A, 6Bare disposed on the opposite side portions of the upper surface of thebed 3, so as to extend in the direction of the X-axis parallel to eachother. A pair of ball nuts 39A, 39B are thread-engaged with the screwshafts 6A, 6B, respectively. To the ball nuts 39A, 39B, the columns 4A,4B are fixed, respectively, whereby the gate-shaped column 11 is movedin the direction of the X-axis according to the axial motion of the ballnuts 39A, 39B along the screw shafts 6A, 6B. A drive motor 40 isdisposed within the bed 3. The drive motor 40 has an output shaftequipped with a pulley 41. The rotation of the pulley 41 is transmittedto a pair of pulleys 42A, 42B, fixed to the respective screw shafts 6A,6B, via a belt 43 wound around the pulleys 41, 42A, 42B, so thatrotations of the pulleys 42A, 42B are synchronized with each other, thusmoving the ball nut 39A, 39B simultaneously. The drive mechanism fordriving the screw shafts 6A, 6B is not particularly limited to theillustrated one. For instance, the screw shafts 6A, 6B may be driven byrespective drive motors directly connected thereto, which motors arecontrolled to provide synchronized operation with each other.

[0129] (c) Two Saddles 8A, 8B Mounted on a Cross Rail (Y1- Axis,Y2-Axis)

[0130] Referring back to FIG. 6A, there is shown a front view of twosaddles 8A, 8B. Two saddles 8A, 8B are mounted on the second guide rails9A, 9B disposed on the cross rail 7 so as to extend over the twosymmetrical columns 4A, 4B in the direction of Y-axis perpendicular tothe Z-axis and the X-axis, as shown by arrows in FIGS. 6A and 6B.Therefore, the two saddle systems 8A, 8B are movable in the direction ofY-axis along the second guide rails 9A, 9B. The two saddle systems 8A,8B are driven by respective drive motors whose operation is controllableso as to place the saddles 8A, 8B at respective desired positions. FIG.8A is a view corresponding to that of FIG. 6A, in which the two saddles8A, 8B are removed from the second guide rails 9A, 9B. As is apparentfrom FIG. 8A, ball-screw shafts 10, 14 are disposed on the cross rail 7so as to extend along with the second guide rails 9A, 9B, i.e., in theY-axis direction. The screw shaft 10 is driven by an Y1-axis controlmotor 47, while the ball-screw shaft 14 is driven by an Y2-axis controlmotor 48. FIG. 8B shows power transmittal members constituting themotors 47, 48.

[0131] As is apparent from FIGS. 8A and 8B, the second guide rails 9A,9B are disposed on the front side surface 7 a of the cross rail 7 so asto extend parallel to each other. Each of the saddles 8A, 8B has fourlinear bearings 49 fixed on the rear surface thereof. The saddles 8A, 8Bare mounted on the second guide rails 9A, 9B at their linear bearings,so that the saddles 8A, 8B are slidably movable along the second guiderails 9A, 9B in the Y-axis direction. Further, the ball-screw shafts 10,14 are also disposed on the front side surface 7 a of the cross rail 7so as to extend parallel to the second guide rails 9A, 9B, which aredriven by the motor 47 (Y1-axis) and the motor 48 (Y2-axis) to make arotational motion. This rotational motion of the screw shafts 10, 14 areconverted into longitudinal motions of nuts 50, 51 along the screwshafts 10, 14, respectively, which nuts 50, 51 are thread-engaged withthe screw shafts 10, 14 and firmly fixed to the rear surfaces of thesaddles 8A, 8B. Therefore, the saddles 8A, 8B are reciprocally moved inthe Y-axis direction in accordance with the longitudinal motion of thenuts 50, 51 caused by the rotation of the screw shafts 10, 14. The motor47 for rotating the screw shaft 10 is operable under control by asuitable control device so that the longitudinal motion of the nut 50,i.e., the displacement of the saddles 8A in the Y1-axis is suitablycontrolled. Likewise, the motor 48 for rotating the drive shaft 14 isoperable under control by a suitable control device so that thelongitudinal motion of the nut 51, i.e., the displacement of the saddles8B in the Y2-axis is suitably controlled. In this respect, the saddles8A, 8B share the same guide rails 9A, 9B, so that the motors 47, 48 aresuitably controlled to prevent interference between the saddles 8A and8B in the Y-axis direction.

[0132] The tool rests 18, 19 disposed on the saddles 8A, 8B may holddifferent kinds of cutting tools, for example. In this case, the saddles8 A, 8B are selectively driven. While the two saddles 8A, 8B aredisposed on the same side, i.e., the front side of the cross rail 7 andutilize the same second rails 9A, 9B for their displacement in theY-axis direction, the structure of the two saddles 8A, 8B are notpartially limited, but may otherwise be modified or changed. Forinstance, the second guide rails 9A, 9B may be provided for each of thetwo saddles 8A, 8B. The saddles 8A, 8B may be disposed on the oppositesides, i.e., the front and rear sides of the cross rail 7, respectively,rather than the same side of the cross rail 7. In the case where thetool units attached to the tool rests 18, 19 may interfere with theother components or devices installed on the bed 3, it is effective tochange arrangement of the saddles 8A, 8B on the gate-shaped column 11,thus avoiding or eliminating the undesirable interfere of the tool unitsand the other components.

[0133] (d) Tool Rests Disposed on the Two Saddles (Z1 Axis, Z2 Axis)

[0134]FIG. 6A shows the tool rests 18, 19 mounted on the saddles 8A, 8Bon the front side of the cross rail 7. FIGS. 9A, 9B show a frontelevational view and a side elevational view of tool-rest supportmechanism in which the tool rest 19 are indicated by a two-dot chainline. Further, FIG. 10 shows one example of the operating state of thetool rest 19 in which a milling cutter unit 59 as a rotative tool 57 isfixed to the tool rest 19. FIG. 11 shows another example of theoperating state of the tool rest 19 in which a drill 82 as the rotativetool 57 is fixed to the tool rest 19. FIG. 12 shows yet another exampleof the operating state of the tool rest 19 in which a single edged tool58 or a multi-edged tool 74 as a fixed tool 69 is fixed to the tool rest19. It should be noted that both of the tool rests 18, 19 may beprovided with various kinds of rotative tools and fixed tools in apossible variety of combinations. The tool rests 18, 19 may also beprovided with the cutting device 77 which will be described later orvarious kinds of groove cutting tools. For instance, the tool rests 18,19 may be provided with the rotative tool 57 and the fixed tool 69,respectively. The tool rests 18, 19 may otherwise be provided withdifferent fixed tools, e.g., the single edged tool 58 and the multiedged tool 74, respectively. Alternatively, the tool rests 18, 19 may beprovided with different rotative tools 57, namely, the tool rest 18 isprovided with one of the milling cutter unit 59 and the drill unit 65,while the tool rest 19 is provided with the other.

[0135] As is apparent from FIG. 9A, a pair of third guide rails 52B aredisposed on the front surface of the saddle 8B so as to extend in theZ-axis direction, while being parallel to each other. The tool rest 19(indicated by the two-dot-chain line) is mounted on the third guiderails 52B via the four linear bearings 53B, whereby the tool rest 19 ismovable along the third guide rails 52B in the Z-axis direction. A screwshaft 12B is also disposed on the front surface of the saddle 8B so asto extend in the Z-axis direction. A ball nut 55B is threaded engagedwith the screw shaft 12B. On the upper end portion of the saddle 8B,there is disposed a motor 13B for driving the screw shaft 12B. Theoperation of the motor 13B is suitably controlled so as to regulate afeed per revolution (i.e., an amount of depth of cut) of a tool fixed tothe tool rest 19. A pair of balancers 56B are also disposed on the upperend portion of the saddle 8B. The presence of the balancers 56B ensuresa stable weight balance of the tool rest 19 in the Z-axis direction,thus ensuring smooth displacement of the tool rest 19 and accuratepositioning control of the tool rest 19. As is understood from theforegoing description, the circular platen 1, the gate-shaped column 11,the saddles 8A, 8B and the tool rests 18, 19 are driven and positionedby suitably controlled operation of the motor 21 for the C-axis control,the motor 40 for the X-axis control, the motors 47, 48 for the Y1-axisand Y2-axis control, and the motor 13A, 13B for the Z1-axis and Z1-axiscontrol, in the present embodiment. These drive motors 21, 40, 47, 48,13A, 13B may be servomotors of a pneumatic type, a hydraulic type, anelectromagnetic type or other possible types.

[0136] In the present embodiment, the gate-shaped column 11 is guided tomove in the X-axis direction by the first guide rails 5A, 5B, and thesaddles 8A, 8B are guided to move in the Y-axis direction by the secondguide rails 9A, 9B, while the tool rests 18, 19 are guided to move inthe z-axial direction by the third guide rails 52A, 52B, as describedabove. Therefore, the cutting edges of the tools fixed to the tool rests18, 19 can be accurately positioned in the above-indicated X, Y andZ-axis directions by utilizing a numerical control device (hereinafterreferred to as “NC” device) 102. Namely, the NC device controls theoperations of the drive motors 21, 40, 47, 48, 13A, 13B so that thepositions of the gate-shaped column 11, the saddles 8A, 8B and the toolrests 18, 19 are accurately controlled. Further, the milling cutter unit59 and the drill unit 65 are selectively detachably fixed to the toolrest 19. FIG. 10 shows one operation state of the grooving machine 10 inwhich the rotative tool 57 consisting of the milling cutter unit 59having a milling cutter 81 (see FIG. 25) is fixed to the tool rest 19.FIG. 11 shows another operation state of the grooving machine 10 inwhich drill unit 65 having a drill 82 (see FIG. 26) is fixed to the toolrest 19.

[0137] There will be described a manner of operation of the groovingmachine of the present invention when the grooving machine is operatedunder control of the NC device 102 for producing the polishing padmultiplicity of straight grooves arranged in the grid pattern, by way ofexample. First, the milling cutter units 59 are fixed to the tool rest18(19). Subsequently, the motor 21 is operated under control of the NCdevice 102 for detecting the current angular position of the circularplaten 1 and then fixing the circular platen 1 in a predeterminedangular position. The motor 40 is also operated under control of the NCdevice 102 for driving the gate-shaped column 11 to a desired positionin the X-axial direction, while the motor 47, 48 are operated undercontrol of the NC device 102 for driving the saddles 8A, 8B in theY-axial direction, while the motors 13A, 13B are operated under controlof the NC device 102 for driving the tool rests 18, 19 to a desiredposition in the Z-axial direction. Thus, the milling cutting unit 59 isaccurately positioned on a desired portion of the foamed urethane pad,which portion is to be processed. With the milling groove cutting unit59 being positioned as described above, the grooving process isperformed according to a suitable processing program stored in a storagedevice of the NC device 102. Namely, a desired amount of depth of cut ofthe milling cutter 81 in the Z-axial direction are provided by theoperation of the motor 13A, 13B under control of the NC device 102,while a desired amount of displacement of feed per revolution of thesaddles 8A, 8B in the Y-axial direction are provided by the operation ofthe motors 47, 48 under control of the NC device 102.

[0138] On the other hand, in the case where the grooving machine isoperated under control of the NC device 102 for forming a through holethrough the foamed urethane pad 15, the drill unit 65 are fixed to thetool rest 18 (19). Like the above case where the grooving machine isoperate to cut the grid-patterned grooves into the surface of the foamedurethane pad 15, the circular platen 1 is placed in the initialposition, while the drill unit 65 is positioned on a portion of theurethane pad 15 which portion is to be processed. According to apredetermined processing program stored in the storage device of the NCdevice 102, the amount of depth of cut of the drill unit 65 in theZ-axial direction is produced by the operation of the motors 13A, 13Bunder control of the NC device 102. The rotation speed of the rotativetool 57 is suitably regulated by controlling the speed of the motor bythe NC device 102.

[0139] When the grooving machine is operated under control of the NCdevice 102 for producing a polishing pad having a multiplicity ofgenerally concentric annular grooves, the fixed tool 69 comprises aselective one of the single edged tool 58 and the multi-edged tool 74 isfixed to the tool rest 18 or 19 (e.g., the tool rest 19 as shown in FIG.12). In this respect, any one of the single edged tool 58 and the multiedged tool 74 may be selected in the light of processing condition, arequired cost of manufacture, or the like. The NC device 102 controlsdisplacements of the gate-shaped column 11 in the X-axis direction, thesaddle 8B in the Y-axis direction, and the tool rest 19 in the Z-axisdirection, so as to place the fixed tool 69 in its initial position.Subsequently, the circular platen 1 is rotated about the C-axis undercontrol of the NC device according to the predetermined control program.The fixing tool 69 is displaced in the Z-axis direction by apredetermined feed per revolution. In order to process all grooves at agenerally constant process speed, the rotating speed of the circularplaten 1 is changed depending upon the position of the fixing tool 69 inthe Y-axis direction.

[0140] While one of the tool rest 19 has been described in detail in theaforementioned description, it should be appreciated that the other toolrest 18 is substantially similar in construction to the tool rest 19.Thus, the same reference numerals as used with respect to elements ofthe tool rest 19 will be used to identify the elements which are thesame as or similar to those in the tool rest 18, and no redundantdescription of elements will be provided, for the sake of simplificationof the description. The grooving machine constructed according to thepresent embodiment, permits that the rotative tool 57 (e.g., millingcutter 81 or drill 82 ) is fixed to one of the tool rests 18, 19 and thefixed tool 69 (e.g., the single edged tool 58 and the multi-edged tool74 ) is fixed to the other one of the tool rests 18, 19. Preferably,these tool units or other various kinds of tool units are easilydetachably fixed to the tool rests 18, 19, thus facilitating interchangeof the tools. This makes it possible to select and use a suitable tooldepending upon a kind of material of the foamed urethane pad 15, andcondition of the cutting, thus assuring a further improved dimensionalor shape accuracy of the formed grooves. It should be understood thatthe motors 21, 40, 47, 48, 13A, 13B may be constituted by linear motorsrather than the illustrated servomotors, for ensuring an high accuracyof positioning and an improved speed of response of the circular platen1, the gate-shaped column 11, the saddles 8A, 8B, the tool rests 18, 19which are moved by these motors in the X, Y1, Y2, Z1, Z2 axes.

[0141] (e) Numerical Control Device to Control Motor and Control Axis

[0142] Numerical control device 102 is adapted to control operation ofthe motors 13A, 13B, 21, 40, 47, 48, so that the circular platen 1, thegate-shaped column 11, the saddle 8A, 8B, the tool rests 18, 19 areaccurately and smoothly positioned in the C, X, Y and X axes,respectively. The numerical control device 102 permits to control themotors 13A, 13B to regulate the feed per revolution of the tool rests18, 19 at minute units. The numerical control device 102 enables anautomatic synchronizing control operation of the plurality of motors,according to a suitable control program that is stored in its storagedevice in advance. In this storage device of the NC device 102, aplurality of grooving patterns to be reproduced on the surface of thefoamed urethane pad 15 are stored in advance. A suitable groovingpattern is selected from the stored grooving patterns, then theoperations of the processing program for the selected grooving patternswith respect to the respective control axes C, X, Y, Z are prepared.According to this predetermined processing program, the grooving machineof this embodiment is automatically operated so as to reproduce theselected grooving pattern on the surface of the polishing pat.

[0143] Referring next to FIG. 13, there is shown a block diagramschematically showing a control system of the NC device 102 adapted tocontrol operation of the grooving machine. Described in detail, the NCdevice 102 includes data input section 101, a central processing unit(CUP) 103, a data storage section 104 and an I/O interface. Uponstarting the grooving process under control of the NC device 102, a toolcommand representing a kind of required tool, and dimensionalinformation of the required tool is applied to the numerical controldevice 102 through the data input section 101. The required tool issuitably determined depending upon a desired groove pattern, e.g., agrid pattern or a generally concentric annular groove pattern. This toolcommand is stored in the data storage section 104 via the CPU 103. Oncean operation command is applied from the input section 101, the CPU 103controls operation of the respective motors 13A, 13B, 21, 40, 47, 48,and the cutting device 77 according to a suitable processing programwith reference to data stored in the storage section 104, so that theoperations of the circular platen 1, the gate-shaped column 11, thesaddles 8A, 8B, the tool rests 18, 19 and the milling cutter unit 59,the drill unit 65 are accurately controlled. Each motor is equipped withan encoder. An amount of rotation of the motor detected by the encoderis applied to the NC device so that the NC device controls the operationof the grooving machine in a feedback control fashion. The CPU 103 alsocontrols operation of the suction blower 25, the position holding member38 of the circular platen 1, the ion blower 114, and a chip collectiondevice 115.

[0144] It should be appreciated that the operation of the groovingmachine may be controllable by utilizing a sequential control device110, instead of the NC device 102 as described above. The use of thesequential control device 110 instead of the numerical control device102 enables to simplify the entire control system and reduce the cost ofthe device, although accuracy of control in positioning, feeding, andcutting are somewhat limited in comparison with that in the numericalcontrol device. 102. Therefore, one of the numerical control device 102and the sequential control device 110 may be optionally selecteddepending upon the use or proccessability of the foamed urethane pad 15.

[0145] Referring next to FIG. 14, there is shown a block diagramschematically showing a sequential control system of the sequentialcontrol device 110 adapted to control operation of the grooving machine.Described in detail, the sequencer device 110 includes an operationpanel 121, a sequencer circuit section 122, a sequential actiondetermining section 123, and a sequencer data output section 124. Uponstarting the grooving process of the grooving machine under control ofthe sequencer device 110, various kinds of data including positionaldata of the control axes and process data with respect to feed perrevolution, an amount of depth of cut, or the like, and a suitablesequential control program representing a predetermined sequence ofprocessing steps, are applied to the sequencer circuit 122 via theoperation panel 121. The sequencer circuit 122 outputs the data receivedfrom the operation panel 121 to the sequential action determiningsection 123 that comprises a sequencer unit and relay circuits. Thesequential action determining section 123 outputs action data to thesequencer data output section 124. The sequencer data output sectionoutputs an action command signal based on the action data to apositioning drive motor 125 operable for controlling positions feedrates, and or depths of cuts of the components arranged in the X, Y1,Y2, Z1, Z2 C axes, a drive motor 126 adapted to drive the rotative tool69, and a drive motor 127 adapted to drive the cutting device 77, sothat these drive motors 125, 126, 127 are operated according to thereceived action command signals. The sequencer data output section 124is operable to generate next action command signals to the drive motors125, 126, 127 each time the operations of these motors 125, 126, 127according to the current command signals are terminated. That is, thesequencer device 110 controls the operation of these drive motors 125126, 127 in an open-loop control fashion. In the present embodiment, thepositioning motors 125, the drive motors 126, 127 may be constituted byutilizing pulse motors. Meanwhile, the grooving machine is provided withvarious kinds of associated equipments 128 including the ion blowingdevice 114, the suction blower 25, the position holding device 38, thechip collection device 115. The operation of the associated equipments128 can be controlled directly through the operation panel 121.

[0146] (f) Ion Blowing Device

[0147] Referring next to FIGS. 15A, 15B, there is shown the ion-blowingdevice 114 adapted to generate and blow positive ions formed by coronadischarge. The ion-blowing device 114 includes a compressed airgenerator (not shown) and a blower nozzle 76, so that the generatedpositive ions are discharged through the blower nozzle 76 together withthe compressed air. Alternatively, the positive ions are dischargedthrough a through holes 71(a) 72(a) which will be described later. Thision-blowing device 114 is disposed in a portion of the grooving machinesuch that a protruded open-end portion of the blower nozzle 76 islocated in the vicinity of the attached cutting tool, e.g., the fixedtool 69 or the rotative tool 57 (the multi-edged tool 74 is attached inFIGS. 15A-15C by way of example). When the foamed urethane pad 15 issubjected to the grooving process, chips of the foamed urethane pad 15are likely to be electrically charged due to friction between thecutting tools and the urethane pad 15, and stick to the surface of theurethane pad 15 and the cutting tools, resulting in difficulty inremoving the charged chips from the surfaces of the cutting tool and theurethane pad. To cope with this problem, the ion blowing device 114 isoperated to blow the positive ions on the chips stick to the cuttingtool and the foamed urethane pad 15, during the grooving process isexecuted for the foamed urethane pad 15, whereby the chips areeffectively neutralized and removed from the cutting tool and theurethane pad 15. When the multi-edged tool 74 of the fixed tool is usedfor forming simultaneously a plurality of grooves on the foamed urethanepad 15, in which a plurality of cutting edges are juxtaposed to eachother, it is required to evenly blow the positive ions on the respectivecutting edges so that the positive ions forcedly come into collisionwith the charged chips. To meet this requirement, the protruded open-endportion of the nozzle 76 may be suitably arranged.

[0148] FIGS. 15A-15C show a front, a side and a bottom elevational viewof the ion-blowing device 114 that is fixed to a tool holder 71. Thetool holder 71 has a rectangular block shape and detachably fixed to theside face of the tool rest 18 (19) by means of suitable fastening meanssuch as a bolt. The tool holder 71 has the above mentioned through hole71 a formed therethrough in the vertical direction as seen in FIG. 15Athrough which positive ions are discharged. To the bottom face of thetool holder 71, a rectangular block shaped tool cartridge is fixed suchthat the tool cartridge 72 is supported by tapered bush 73 so as to bepositioned in the vertical direction as seen in FIG. 15A. The toolcartridge 72 has the above-indicated plurality of straight holes 72 aextending therethrough in the vertical direction as seen in FIG. 15A.These straight holes 72 a are held in communication with the throughhole 71 a of the tool holder 71, so that the lower end of the throughholes 71 a is exposed to the atmosphere through the straight holes 72 a.

[0149] As shown in FIG. 15A, the multi edged tool 74 is fixed to thetool holder 71 by way of example. The multi edged tool 74 may be a tooldetachably installable on the tool holder 71 with high accuracy. Forinstance, the multi edged tool 74 is fixed to the tool cartridge 72. Thecartridge 72 is positioned relative to the tool holder 71 by means oftapered bushes 73, 73. The cartridge 72 is guided by the side walls ofthe tool holder 71, and is firmly fitted to the tool holder 71 by meansof a pressing plate 75 that is bolted to the tool holder 71. Thepositive ions can be discharged from the side of the attached toolthrough the nozzle 76. In the case where the multi edged tool 74 isattached to the tool holder 71 as described above with the compressedair, the ion blowing device 114 may be arranged to blow the positive ionthrough the through hole 71 a formed through the tool holder 71 and thestraight holes 72 a formed through the cartridge 72 instead of or inaddition to the nozzle 76. In the ion-blowing device 114, the compressedair generator may be disposed within the nozzle 76, or the straightholes 72 a, for example. Alternatively, the compressed air generator maybe constituted by utilizing an external compressed air source that isheld in fluid communication with the nozzle 76 or the like via an airconduit. It should be appreciated that the compressed air generator isinterpreted to mean the overall structure thereof including the airconduit connecting between the external compressed air source and thenozzle 76 or the like.

[0150] Instead of the multi-edged tool 74, the single edged tool 58, andthe rotative tool such as the milling cutter unit 59 and the drill unit65 may be mounted on the tool holder 71, likewise. In this case, theblowout of the ion may be possibly executed through the nozzle 76. Itshould be understood that the construction of the blower passage of theion blow device 114 is not limited to the above, but may otherwise bemodified, as needed.

[0151] (g) Fixed Tool (Turning Tool/Cutting Tool)

[0152] (1) Turning Tool (Single Edged Tool and Multi Edged Tool)

[0153]FIGS. 16A and 16B show a front and a side elevational view of thesingle edged tool 58 as one example of the fixed tool 69. FIGS. 17A-17Cshows a bottom, a front and a side elevational view of the multi edgedtool 74 as another example of the fixed turning tool 69. The single edgetool 58 and the multi edged tool 74 are suitably used for the groovingprocess in which the plurality of generally concentric annular groovesare formed on the surface of the foamed urethane pad 15.

[0154] The single edged tool 58 has a cutting part 58 a that is arrangedas follows so that the single edged tool 58 is suitable for cutting aworking piece made of a resin material, e.g., a foamed urethane pad.Namely, the cutting part 58 a of the single edged tool 58 has a toothwidth: W1 within a range of 0.005-1.0 mm, a side clearance angle: θ1within a range of 0-2 degrees, as shown in FIG. 16A. Further, thecutting tooth of the single edged tool 58 has a wedge angle: θ2 within arange of 30-35 degrees, a rake angle: θ3 within a range of 10-20, and afront clearance angle θ4 within a range of 45-55 degrees, as shown inFIG. 16B. These angles of respective parts of the cutting part 58 a ofthe single edged part 58 a are determined taking into account a problemof interface between the cutting part 58 a and walls of the foamedgrooves and a required strength of the cutting part 58 a. Preferably,the single edged part 58 a is made of a rigid material, such as hardmetal, high speed steel, carbon steel, ceramics, cermet, and diamonds.

[0155] As shown in FIGS. 17A-17C, the multi-edged tool 74 has a thinrectangular plate-like shape and includes a plurality of cutting parts58 a integrally formed on and protruding from its bottom end as seen inFIG. 17A, such that the plurality of cutting parts 58 a are arranged ina longitudinal direction of the multi-edged tool 74 at regular intervalswithin a range of 0.2-2.0 mm, over a substantially entire area of thebottom end of the multi-edged tool 74. It is noted that each of theplurality of cutting parts 58 a of the multi-edged tool 74 isdimensioned identically with the cutting part 58 a of the single edgedtool 58. That is, the multi-edged tool 74 serves as a tool tip having aplurality of cutting parts 58 a integrally formed in the end portionthereof.

[0156] Referring next to FIGS. 18 and 19, there is shown by way ofexample the multi-edged tool 74 in the form of the tool tip, which isfixed to the bottom end portion of the tool holder 71, such that themulti-edged tool 74 is gripped by and between the tool holder 71 and thepressing plate 75. Positioning pins 73 fitted to the multi-edged tool 74is used for positioning the multi-edged tool 74 relative to the toolholder 71. The tool holder 71 equipped with the multi-edged tool 74 asshown in FIG. 19, may be solely fixed to the tool holder 18 (19).Alternatively, a plurality of tool holders 71 each equipped with themulti-edged tool 74 may be fixed to the tool holder 18(19), as shownFIG. 20. In this case, the cutting parts 58 a of the plurality ofmulti-edged tools 74 may be arranged at regular intervals, thuspermitting high efficiency in cutting a plurality of grooves on thefoamed urethane pad 15. As is apparent from FIG. 21, it may be possibleto fixed a plurality of multi-edged tools 74 to the tool holder 71 suchthat the cutting parts 58 a are arranged at regular intervals. Thisarrangement facilitates the formation of the plurality of grooves on thefoamed urethane pad 15, likewise.

[0157] Referring next to FIGS. 22, 23, there are schematically shownanother type of multi-edged tools 92, 95 according to the presentinvention by way of example. As is apparent from FIG. 22, themulti-edged tool 92 includes a plurality of cutting tips 90 each havinga single cutting part 58 a. The plurality of cutting tips 90 aresuperposed on each other and are detachably fixed together and fixed tothe lower end portion of the tool holder 71 by means of bolts 91 suchthat the cutting tips 90 are spaced apart from each other with regularintervals in the width direction of the tool holder 71. As is apparentfrom FIG. 23, the multi-edged tool 95 includes a plurality of cuttingtips 93 each having a single cutting part 58 a. Unlike the multi-edgedtool 92, the cutting tooth tips 93 are superposed on each other withspacers 94 interposed between adjacent ones of the cutting tooth tips93. The presence of the spacers 94 makes it easy to keep the spacingbetween adjacent ones of the cutting tooth chips 93 constant. Thelamination consists of the plurality of cutting tooth tips 93 and thespacers 94 interposed between adjacent ones of the cutting tips 93 aredetachably fixed together and fixed to the lower end portion of the toolholder 71 by means of bolts 91. The thus constructed multi-edged tools92, 95 permit an effective muss-production of the tools, an improvedflexibility for a change of the pitch and an ease replacement of thecutting parts 58.

[0158] (2) Cutting Tool

[0159] Referring next to FIGS. 24A-24C, there are respectively shown aside elevational view, a front elevational view and a cross sectionalview taken along line C-C of FIG. 24B of the cutting device 77 which isadapted to be mounted on the tool rest 18 (19) disposed on the saddle 8A(8B) of the cutting machine constructed according to the presentembodiment. The cutting device 77 is operable to cut primary peripheralportion of the foamed urethane pad 15 to shape the external form of thefoamed urethane pad 15 desirably. More specifically described, thecutting device 77 includes: a base 78; a fourth guide rails 63A, 63Bdisposed on the base 78 so as to extend parallel to each other in theZ-axis direction; a tool rest 64 disposed on the base 78 via the pair offourth guide rails 63A, 63B so as to be movable in the Z-axis direction;a cutting tool holder 66 mounted on the tool rest 64; and a power source62 disposed on the base 78 so as to generate a drive power by which thetool rest 64 is moved in the Z-axis direction. A cutting tool 61 isfixed to the cutting tool holder 66 such that a base portion of thecutting tool 61 is fitted into a cutting tool base 83 formed in thecutting tool holder 66, while being supported by the a pair of toolsupports 65 with its protruding end portion supported by a stopper pin80. An output member of the power source 62 is connected to a supportmember 67 disposed on the tool rest 64 via a connecting metal member 68,thus transmitting output power of the power source 62 to the tool rest64. Thus, the cutting tool 61 is driven in the Z-axis direction. Itshould be understood that the power source 62 may comprises apiston-cylinder mechanism of pneumatics type or hydraulic type, or asolenoid-type actuator. It should be further understood that the cuttingtool 61 may otherwise be constituted by a suitable turning tool forassuring further improved cutting ability of the cutting device 77.

[0160] (h) Rotative Tool (Milling Cutter and Drill)

[0161] (1) Milling Cutter

[0162]FIG. 25A shows a front view of one example of a milling cutter 81for forming a fine groove, which is fixed to the grooving milling cutterunit 59. FIG. 25B shows an enlarged view of cutting parts 79 of themilling cutter 81 of FIG. 25A. The milling cutter 81 is a thin circulardisk member, which has a center hole 81 a formed therethrough and aplurality of cutting part 79 integrally formed in its outer peripheralportion such that the plurality of cutting part 79 are arranged in acircumferential direction of the grooving milling cutter 81 with auniform pitch. Each of the cutting parts 79 is dimensioned to have awedge angle: θ5 within a range of 20-45 degrees, since the wedge angle:θ5 smaller than 20 degrees may cause undesirable shortening of the lifeof the grooving milling cutter 81, while the wedge angle: θ5 larger than45 degrees may cause deterioration of cutting capability of the cuttingtooth 79. Further, the each cutting parts 79 is dimensioned to have arake angle: θ6 within a range of 30-40 degrees, more preferably ataround 30 degrees, since the rake angle: θ6 smaller than 30 degrees maycause deteriorated stability of the milling cutter 81, while the rakeangle: θ6 larger than 40 degrees may cause deterioration of cuttingcapability of the cutting tooth 79. Yet further, the each cutting tooth79 is dimensioned to have a side cutting edge angle within a range of0-2 degrees and a tooth width within a range of 0.3 mm-2.0 mm. The thusformed milling cutter 81 is disposed radially outwardly on a tool shaftformed on the lower portion of the grooving milling cutter unit 59 androtated in a predetermined circumferential direction by the drive motor126. The number of the milling cutter 81 fixed to the tool shaft is notparticularly limited. For instance, a plurality of grooving millingcutters 81 may be fixed to the tool shaft with constant intervals withina range of 0.1 mm or more, so that a plurality of grooves arranged in agrid pattern are formed on the foamed urethane pad 15 with improvedefficiency.

[0163] (2) Drill

[0164]FIG. 26A shows a front elevational view of one example of a drill82 to be fixed to the drill unit 65, and FIG. 26B shows an exploded viewof a cutting part 82 a of the drill 82. As shown in FIG. 26A, the drill82 has a diameter: D1 within a range of 0.5 mm-1.5 mm and a length: L1within a range of 20-30 mm. As shown in FIG. 26B, the cutting part 82 aof the drill 81 includes two cutting edges 83, 83. The end edge portionof the drill 82 has a cone angle θ8 within a range of 55-65 degrees,more preferably at around 60 degrees, thus assuring a smooth insertingof the drill 81 into the work piece. A helix angle: θ7 of the twocutting edges 83, 83 is arranged to be held within a range of 1-10degrees, preferably at about 5 degrees. This arrangement makes itpossible to gradually cut a part of the foamed urethane pad 15 locatedaround the edge of the drill 82, thereby forming a desired hole having apredetermined diameter. The number of the drill 82 fixed to the drillunit 65 is not particularly limited. For instance, a plurality of drill82 may be fixed to the drill unit 65 to form a multi-shaft type drillunit, so that a plurality of holes are formed into the foamed urethanepad 15 with improved efficiency.

[0165] There will be described a method of producing a multiplicity ofgrooves on the surface of the foamed urethane pad 15 by using thegrooving machine constructed according to the present invention by wayof example.

[0166] (i) Concentric Fine Grooves

[0167] Referring next to FIGS. 27A, 27B, there is shown a polishing padfabricated according to one preferred embodiment of the invention by wayof example. The polishing pad is formed by cutting a multiplicity ofgenerally concentric grooves into the surface of the foamed urethane pad15 having a thickness: T1 within a range of 1.0 mm-2.0 mm. The generallyconcentric grooves have a width: W1 within a range of 0.005-1.0 mm, adepth: D1 within a range of 0.2-2.0 mm, and a pitch: L2 within a rangeof 0.2-2.0 mm. For producing the polishing pad of the present invention,initially, the single-edged cutting tool 58 or the multi-edged cuttingtool 74 is fixed to the tool rest 18(19), while a base for desiredpolishing pad, e.g., the foamed urethane pad 15 is placed on the suctionplate 16 of the circular platen 1. Preferably, the foamed urethane pad15 is shaped to have a circular-disk shape identical in size with thecircular platen 1 in advance, by cutting. The cutting of the foamedurethane pad 15 may be executed by means of cutting device 77 fixed tothe tool rest 18 (19). In the case where the foamed urethane pad 15 hasa diameter smaller than the suction plate 16, an annular covering membermay be placed on the outer peripheral portion of the suction plate 16located radially outward of the foamed urethane pad 16, so that the airholes 16 a open in the outer peripheral portion of the suction plate 16is effectively closed by the annular covering member. The suction plate16 may be modified so that only a portion of the suction plate 16serving for suctioning the urethane pad 15 is provided with the airholes 16 a. Alternatively, the communication grooves 16 b formed in thesuction plate 16 may be partially closed so that distribution of thesuction force on the suction plate 16 is divided into local sections.

[0168] With the base for the foamed urethane pad 15 placed on thecircular platen 1 as described above, the suction blower 25 is operated,whereby the base for the foamed urethane pad 15 is firmly fixed on thecircular platen 1 by the suction force applied on the rear surfacethereof. A predetermined revolution speed of the circular platen 1 aboutthe C-axis during the grooving operation is set in advance to a suitablecontrol device such as the NC device 102 and the sequential controldevice 110 so that every groove is cut at the same turning speed. Thegate-shaped column 11, the saddle 8A (8B) and the tool rest 18 (19) aremoved to be placed in their initial positions in the X-axis, Y-axis andZ-axis directions, respectively, under control of the suitable controldevice. In addition, radial positions of the respective generallyconcentric annular grooves are determined in the Y-axis directiondepending upon the number of grooves cut into the surface of the foamedurethane pad 15 according to control program of the control device. Apredetermined amount of displacement of the tool rest 18 in the Z-axisdirection is set to the control device in advance so as to control anamount of depth of cut of the single edged tool 58. Thus, the cuttingdevice is on standby. Upon starting cutting, the rotation of thecircular plate 1 about the C-axis is started at the predeterminedrevolution speed. The cutting by tool 58 is started at the predeterminedamount of depth of cut. Namely, the tool 58 executes a predeterminednumber of cuttings by the slight amount of depth of the cut, therebycutting one fine annular groove into the surface of the base for thefoamed urethane pad 15.

[0169] The tool rest 18 and the saddle 8A is subsequently displaced inthe Y-axis direction so as to subsequently form the multiplicity ofgrooves. When the formed urethane pad has a relatively large area and agreat number of grooves are required to be formed, the multi-edged tool74 is preferably employed. The multi-edged tool 74 may consist of 10-30single-edged tools juxtaposed to each other, for example. The use of themulti-edged tool 74 makes it possible to form a great number of grooveswith high efficiency.

[0170] Meanwhile, the cutting of the grooves into the formed urethanepad 15 causes a problem of chips. Namely, the kind or shape of thecutting chip may vary depending upon materials of the base of thepolishing pad pieces. For instance, the chips may be a powder form or aribbon form. In particular, the cutting chip is likely to beelectrically charged, and accordingly to be adhered to the urethane pad15, the cutting tool, e.g., the single edged tool 58 or the like. Thismakes it difficult to assure a complete removal of the cutting chip byonly executing air blowing. To cope with this problem, the groovingmachine of the present embodiment is equipped with the ion blower. Theion blower is operated to discharge positive ions, which are chargedenough to neutralize the chips, through the nozzle open in the vicinityof the cutting part of the tool 58, thus neutralizing the electricallycharged chips by the positive ions, resulting in an desired removal ofthe cutting chips from the urethane pad 15 and the single-edged tool 58.Preferably, a nozzle of a suitable vacuum system is disposed in thevicinity of a cutting portion of the urethane pad so as to vacuum thecutting chips from the cutting portion, to thereby prevent undesirabledisperse of the cutting chips. This arrangement is effective to executethe grooving process with high accuracy. The synchronization of themotions of the single cutting tool 58 in the Z-axis direction, thesaddle 8A (8B) in the Y1 (Y2)-axis direction and the circular platen 1about the C-axis enables to form a swirl groove on the foamed urethanepad 15. After the grooving process is terminated, the cutting device 71may be usable to cut the circular urethane pad 15.

[0171] (j) Grid Patterned Fine Grooves

[0172] Referring next to FIG. 28, there is shown one example of apolishing pad having a plurality of grooves arranged in the gridpattern. This polishing pad is formed by cutting a multiplicity ofstraight grooves arranged in the grid pattern into the base for thepolishing pad, e.g., the foamed urethane pad 15 having a thickness of1.4 mm. Each of the straight grooves has a width of 0.8 mm, a depth of0.5 mm and a pitch of 6.35 mm. For producing this grid grooved polishingpad, initially, the rotative tool unit 57 equipped with the millingcutter 81 is fixed to the tool rest 19 disposed on the saddle 8B, whilethe urethane pad 15 as a working piece is placed on the circular platen1. Subsequently, the angular position of the circular platen 1 about theC-axis is detected, and then the circular platen 1 is held in itsinitial angular position, under control of suitable control device,e.g., the NC device 102 or the sequencer 110. For forming the grooves inthe grid pattern, the circular platen 1 placed in its initial angularposition is then rotated about the X-axis by 90 degrees to be held inits first processing angular position. The gate-shaped column 11, thesaddle 8B and the tool rest 19 are moved to be placed in their initialpositions in the X-axis, Y-axis and Z-axis directions, respectively,under control of the control device. A predetermined pitch ofdisplacement of the gate-shaped column in the X-axis in the grid patternis set in advance, thus eliminating a need for a surplus displacement ofthe tool rest 19 in the Y-axis direction.

[0173] With the circular platen 1 being held in its first processingangular position, and with the tool rest 19 held in its initialposition, the process for cutting the grid-patterned grooves isinitiated. The gate-shaped column 11 is subsequently moved in the X-axisdirection by the predetermined pitch of displacement corresponding tothe pitch of the grid-patterned grooves, each time one straight grooveis formed, whereby a multiplicity of straight grooves extending parallelto each other are formed on the urethane pad 15. After a desired numberof straight grooves is formed on the surface of the foamed urethane pad15 positioned in the first processing angular position of the circularplaten 1, the circular platen 1 is then rotated about the C-axis by 90degrees so as to be placed and held in its second processing angularposition. Then, a predetermined number of grooves are formed on thesurface of the urethane pad 15 so as to extend parallel to each otherand cross the previously formed grooves at right angles. Thus, thedesired grid grooves polishing pad is obtained. Upon cutting the grooveson the foamed urethane pad 15 by using the milling cutter 81, the chipsin the form of powder are produced and dispersed around the cutting partof the urethane pad 15 and are likely to be adhere to the urethane pad15 and the milling cutter 81. Therefore, the above-described ion-blowingdevice 114 should be employed.

[0174] (k) Radial Grooves

[0175] The grooving machine constructed according to the presentinvention may form radially arranged grooves on the base for thepolishing pad, e.g., the foamed urethane pad 15. Described morespecifically, the circular platen 1 on which the foamed urethane pad 15as the work piece is fixedly placed, is held in a processing angularposition, and then the milling cutter 81 fixed to the tool rest 19 ismoved by a predetermined amount in the Y-axis direction so as to form asingle straight groove extending in a radial direction of the urethanepad 15. After the single radial groove is formed, the circular platen 1is rotated by a predetermined angle so as to be held in a nextprocessing angular position thereof. The grooving milling cutter 81 ismoved again by the predetermined amount in the Y-axis direction so as toform another single straight grooves extending in a radial direction ofthe urethane pad 15. The above described reciprocating motion of thegrooving milling cutter 81 in the Y-axis direction and the rotation ofthe circular platen 1 about the C-axis are repeated until a desirednumber of grooves are formed on the urethane pad 15. Thus, the polishingpad having the radial grooves is obtained. In this case, the use of theion blower is preferable.

[0176] The above described radial grooves may be formed on the foamedurethane pad 15 which has a multiplicity of generally concentric annulargrooves. Further the above-described radial grooves may be modified soas to form a polishing pad 200 constructed according to anotherembodiment of the invention, as shown in FIG. 29. The polishing pad 200has curved radial grooves 202. To form this polishing pad, an knownendmill (not shown) is fixed to the drill unit 65. The circular platen 1is controlled to be rotated about the C-axis at a predeterminedrevolution speed and by a predetermined amount of angle, while beingsynchronized with the feed of the tool rest 19 in the Y-axis direction.Thus, the desired polishing pad 200 having curved radial grooves 202 isobtained.

[0177] (m) Drilling

[0178] The obtained polishing pads as described above, may be subjectedto a drilling process as needed. The drilling process makes it possibleto form a plurality of fine holes through the polishing pads. Thedrilling process may be performed on a working piece that is notsubjected to any grooving process. In order to perform the drillingprocess, a special drill 82 is fixed to the drill unit 65 mounted on thetool rest 19, initially, Subsequently, the circular platen 1 ispositioned about the C-axis, and the gate-shaped column 11, the saddle8B and the tool rest 19 are respectively positioned in the X-axis,Y-axis and Z-axis directions. Then, the tool rest 19 is moved downwardlyin the Z-axis direction by a predetermined amount of feed, assuring apredetermined amount of depth of cut of the drill 82. Thus, a desiredhole is formed through the grooved urethane pad or the work piece.

[0179] The grooving machine may be operated under control of thesuitable control device to form automatically the plurality of holes onthe base for the polishing pad on the basis of coordinate values in theX, Y, and Z axes each representing a portion of the hole to be formed onthe surface of the base for the polishing pad, which are stored in thememory of the control device in advance. Since the end of the drill 82has a conical shape and has no cutting edge, the drill 81 is initiallycompresses the base for the polishing pad by the conical shaped edge,and then gradually cut the compressed part of the polishing pad by thecutting edge 58 a formed in a body portion of the drill 81, whereby thedrill 81 is able to be smoothly inserted into the inside of the base forthe polishing pad. Thus, the drill 82 is able to form a desired holeeven when the base for the polishing pad is made of a soft material,such as a foamed urethane. In the light of the fact that the workingpiece for forming the polishing pad has a relatively small thickness,the suction plate 16 may be formed with recesses at portionscorresponding to the portions of the base for the polishing pad in whichthe holes is formed by drilling. The diameter of the recess is madelarger than the diameter of the drill 81. This arrangement makes itpossible to effectively guide the conical shaped edge of the drill 81,and to facilitate forming the through holes by drilling on the base forthe polishing pad such as the foamed urethane pad. In the drillingprocess, the use of the ion blower is preferable for facilitatingremoval of the chips.

[0180] While the presently preferred embodiments of this invention hasbeen described above by reference to the accompanying drawings, forillustrative purpose only, it is to be understood that the presentinvention is not limited to the details of the illustrated embodiments,but may be otherwise embodied.

[0181] For instance, single edged tool may be arrange to have a cuttingpart which is curved arcuately in its width direction. The opposite endportions of the curved cutting part may be protrude outward of anintermediate portions interposed between the opposite end portions inthe width direction. The single edged tool may be otherwise arranged tohave a tip portion being serrated, namely to have a saw-toothed cuttingpart. The side surfaces of the cutting part may be serrated, as needed.

[0182] While the grid patterned grooves are formed on the surface of thebase for the polishing pad by using a milling cutter 81 in the groovingmachine of the illustrated embodiment, the grid patterned grooves may beformed more efficiently by utilizing a single edged tool or a multiedged tool that is fixed to the tool rest 18 (19) that is reciprocallymovable in the Y-axis direction at a relatively high speed, e.g., 50-180m per minute. More specifically described, the grooving machine ismodified such that the saddles 8A, 8B are reciprocally moved in theY-axis direction by means of linear motors disposed so as to extendalong the guide rails 9A, 9B, instead of the ball-screw shafts 10, 14.The use of the linear motors enables the above-indicated high-speedreciprocal motion of the saddles 8A, 8B and the tool rest 18, 19 in theY-axis direction, in comparison with the ball-screw shafts 10, 14 whichpermits the reciprocal movement of the saddles 8A, 8B at 10 m per minuteat most. Thus, the modified grooving machine, which has the linearmotors as a drive power source of the saddles 8A, 8B in the Y-axisdirection, is capable of cutting the grid patterned grooves into thebase for the polishing pad with significantly improved efficiency. Inaddition, the modified grooving machine utilizes the single or multiedged tool rather than the milling cutter 81. This arrangement iseffective to prevent undesirable melt of the base of the polishing paddue to heat caused by frictional contact of the milling cutter 81 withthe base for the polishing pad, depending upon kinds of materials of thebase for the polishing pad.

[0183] It is also to be understood that the present invention may beembodied with various other changes, modification and improvements,which may occur to those skilled in the art, without departing from thespirit and scope of the invention defined in the following claims.

EXAMPLES

[0184] To further illustrate the present invention, there will bedescribed some examples of the invention. It is to be understood thatthe invention is not limited to the details of these examples, but maybe embodied with various changes, modifications and improvements, whichmay occur to those skilled in the art, without departing from the spiritand scope of the invention defined in the appended claims.

[0185] There were prepared two specimens of the polishing pad accordingto Examples 1 and 2 of the present invention as shown in FIGS. 30, 31 bycutting multiplicity of generally concentric annular grooves 130 intosurfaces of respective foamed urethane pads 15 by using respectivemulti-edged tools 74 each constructed according to the present inventionas indicated in the following Table 1. Described in detail, each of thespecimens of Examples 1 and 2 is formed by using the grooving machine ofthe present invention. The foamed urethane pad 15 attracted on thesuction plate 16 of the circular platen 1 is rotated about the C-axis ata speed of 150 revolutions per minute, and the multi-edged tool 74 fixedto the tool rest 18 is cut into the foamed urethane pad 15 at a feed perrevolution of 0.01 mm/rev. The prepared specimens of the polishing padof the Examples 1 and 2 had grooves 130 whose dimension were held withina range of the invention, as indicated in Table 1.

[0186] On the other hand, specimens of the polishing pads constructedaccording to comparative examples 1 and 2 were prepared by using anoptional multi-edged tool having a plurality of cutting parts whoseshape does not meet the requirements of the present invention asindicated in Table 1. Each specimens of the polishing pad of thecomparative examples 1 and 2 were formed in the same processingcondition as described above with respect to the specimens of theExamples 1 and 2. Dimensions of the grooves 130 of the obtainedspecimens of the comparative examples 1 and 2 were also indicated inTable 1.

[0187] Microscopic photographic view of cross sections of the obtainedspecimens were obtained and evaluate qualities of the grooves 130 of theobtained specimens in terms of occurrence of burrs, occurrence of dullededge of the grooves, and occurrence of raised portions on the surface ofthe pad. The results were also indicated in Table 1. It is noted thatthe evaluated grooves have radius of curvatures at around 50 mm. In thisrespect, FIG. 32A shows a microscopic photographic view of 30 timesmagnification and FIG. 32B is a microscopic photographic view of 100times magnification in axial cross section of the groove formed on thepolishing pad of the Example 1. On the other hand, FIGS. 33A, 33Bcorrespond to the FIGS. 32A, 32B, in which the groove formed on thepolishing pad of the comparative example 1 is shown in its axial crosssection. FIG. 34 is a microscopic photographic view of 60 timesmagnification showing a cross sectional shape of a groove of the Example2 of a polishing pad of the invention; and FIG. 35 is a microscopicphotographic view of 120 times magnification showing a cross sectionalshape of a groove of the comparative example 2 of a polishing pad. TABLE1 Com- Com- parative partive Example 1 Example 2 Example 1 Example 2Tool Tooth Width 0.35 0.15 0.35 0.15 Shape (mm) Wedge angle 35° 35° 60°60° Front 45° 45° 20° 20° Clearance Angle Groove Groove 0.3 0.1 0.3 0.1Shape Width (mm) Groove 0.5 0.3 0.4 0.4 Depth (mm) Groove 2.0 0.5 1.11.0 Pitch (mm) Groove Burrs None Almost Occurred Occurred Condition noneDulled None None — — Edges Raised None Almost Occurred Occurred Portionsnone Quality Good/Bad Good Good Bad Bad

[0188] As is understood from Table 1, the polishing pads of the Examples1 and 2 which were formed by using the multi edged tool 47 havingcutting parts whose dimensions are held within a range of the invention,have a desired shape and never suffer from the problem of occurrence ofburrs, dulled edges and raised portions. Therefore, the specimens of thepolishing pads according to Examples 1 and 2 are capable of establishinga desired distribution of a slurry, and exhibiting a desired polishingeffect. Further, the grooves 130 of the specimens of the polishing padsof Examples 1 and 2 were formed with high dimensional accuracy, thuseliminating or minimizing the conventionally experienced problem ofvariation in width of the grooves 130 after execution of the dressingprocess of the polishing pad. Further, the specimens of the polishingpads of Examples 1 and 2, have accurately dimensioned grooves atradially inner portions thereof as shown in FIG. 36. In FIG. 36, thegrooves have radius of curvatures within at around 1.0 mm. Therefore,the specimens of the polishing pads of Examples 1 and 2 is able tominimize radially inner useless areas thereof.

[0189] On the other hand, the polishing pads of the comparative examples1 and 2, which were formed by using the multi-edged tool having thecutting parts whose dimensions were not held within the range of theinvention, suffer from occurrence of burrs and dulled edges. Therefore,the specimen of the polishing pad of the comparative examples 1 and 2are incapable of exhibiting a desired polishing effect with stability,and are likely to suffer from variation in the width of the groovesafter execution of the dressing process of the polishing pad.

[0190] To further clarify technical advantages of the present invention,a relationship between variation in a groove width and a variation of anabutting pressure of a polishing pad with respect to a work, i.e., awafer, were obtained by conducting a simulation using a static model asshown in FIG. 37. Where a groove width: “a” varies among four values:0.2 mm, 0.2375 mm, 0.2625 mm and 0.3 mm while a groove pitch is madeconstant, a variation of the abutting pressure of the polishing padapplied on a surface of the wafer were calculated according to thefinite element method. The obtained result as shown in graphs of FIGS.38 and 39.

[0191] As is understood from the graph of FIG. 38, the abutting pressureof the polishing pad applied on the surface of the wafer issignificantly increased at open-end edge portions of each groove.Namely, a significantly high peak pressure is generated at the open-endedge portions of the each groove. As is also understood from the graphof FIG. 39, the peak pressure varies over 1.0 gf/mm² or more under thecondition of a groove width variation or error of ±20%. In the casewhere the each groove has a relatively small width selected from apredetermined groove width range of 0.005-1.0 mm of the presentinvention, the groove width error of ±20% means a dimensional differencewithin a range of 0.002-0.40 mm. This clearly shows that a highdimensional accuracy of the grooves is significantly important to assurea desired polishing ability of the polishing pad with high stability. Itshould be appreciated that conventional technique for grooving thepolishing pad is absolutely insufficient to form such a finemultiplicity of circumferential grooves on the base for the polishingpad with high dimensional accuracy. The aforementioned high dimensionalaccuracy of the grooving technique of the present invention should beappreciated as a prominence effect of the present invention, which isdistinguishable from the conventional grooving techniques.

What is claimed is:
 1. A turning tool for cutting circumferentialgrooves into a surface of a polishing pad formed of a resin material andutilized for polishing semiconductor devices, said turning toolcomprising: a cutting part arranged to have a tooth width within a rangeof 0.005-1.0 mm, a wedge angle within a range of 15-35 degrees, and afront clearance angle within a range of 65-45 degrees.
 2. A turning toolaccording to claim 1, wherein said cutting part has a rake angle withina range of 20-10 degrees.
 3. A turning tool according to claim 1,wherein said cutting part has a side clearance angle with respect to aradially outer wall of each of said grooves, which is held within arange of 0-3 degree.
 4. A turning tool according to claim 1, whereinsaid turning tool includes a plurality of cutting parts which arearranged in a predetermined direction with a pitch within a range of0.2-2.0 mm.
 5. A turning tool according to claim 4, wherein saidplurality of cutting parts are arranged in a predetermined directionwith regular pitches.
 6. A turning tool according to claim 4, furthercomprising a plate-like shaped tool tip having a plurality of cuttingparts integrally formed at one of edge portions thereof so as toprotrude outwardly from said one of said edge portions.
 7. A turningtool according to claim 6, wherein said turning tool comprising aplurality of said tool tips, said tool tips being fixedly arranged witheach other so as to be aligned in a width direction thereof, saidcutting parts of said plurality of tool tips cooperate to form amultiplicity of cutting parts.
 8. A turning tool according to claim 7,further comprising a predetermined tool-tip holder to which saidplurality of said plate-like shaped tool tips are detachably fixed, saidtool tip holder and said plurality of tool tips cooperate to constitutea tool unit.
 9. A turning tool according to claim 4, further comprisinga plurality of cutting tips each having one of said cutting parts, saidplurality of cutting tips are detachably fixed to each other so thatcutting parts of said plurality of cutting tips cooperate to form aplurality of cutting parts.
 10. A turning tool according to claim 9,wherein said plurality of cutting tips are superposed on and integrallyfixed to one another with spacers interposed adjacent ones of thecutting tips so that the spacers function to keep a pitch of saidplurality of cutting tips.
 11. A turning tool according to claim 9,further comprising a cutting-tip holder to which the plurality ofcutting tips are detachably fixed, said cutting tip holder and saidcutting tips cooperate to constitute a unit tool.
 12. A turning toolaccording to claim 10, further comprising a cutting-tip holder to whichthe plurality of cutting tips are detachably fixed, said cutting tipholder and said cutting tips cooperate to constitute a unit tool.
 13. Aturning tool according to claim 1, wherein said cutting part has a tipportion arcuately curved in a width direction thereof so that said tipportion has two end parts opposed in said width direction, said two endparts of said tip portion protruding outwardly from an intermediate partof said tip portion in a direction perpendicular to said widthdirection.
 14. A turning tool according to claim 1, wherein said cuttingpart has a tip portion being serrated.
 15. A turning tool according toclaim 1, wherein said cutting part has at least one side surface beingserrated.
 16. A method of producing a polishing pad made of a resinmaterial, comprising the steps of: positioning a turning tool comprisinga cutting part arranged to have a tooth width within a range of0.005-1.0 mm, a wedge angle within a range of 15-35 degrees, and a frontclearance angle within a range of 65-45 degrees, relative to a base forsaid polishing pad formed of said resin material; rotating said cuttingpart of said turning tool relative to said base for said polishing padabout an axis of said base for said polishing pad, for cuttingcircumferential grooves into a surface of said base such that radiallyinner most one of said circumferential grooves has a radius of curvatureof 10 mm or smaller.
 17. A method of producing a polishing pad accordingto claim 16, wherein said turning tool comprises a plurality of cuttingparts which are arranged in a predetermined direction with a pitchwithin a range of 0.2-2.0 mm, and wherein said circumferential groovescomprises a multiplicity of generally concentric annular grooves, saidmethod further comprising the steps of: simultaneously cutting aplurality of said generally concentric grooves into said surface of saidbase for said polishing pad such that radially inner most one of saidmultiplicity of generally concentric annular grooves has a radius ofcurvatures of 10 mm or smaller.
 18. A method of producing a polishingpad according to claim 17, wherein said plurality of cutting parts arearranged in a predetermined direction with regular pitches.
 19. A methodof producing a polishing pad according to claim 16, wherein said turningtool comprises a plate-like shaped tool tip having a plurality ofcutting parts integrally formed at one of edge portions thereof so as toprotrude outwardly from said one of said edge portions and arranged in apredetermined direction with a pitch within a range of 0.2-2.0 mm, andwherein said circumferential grooves comprises a multiplicity ofgenerally concentric annular grooves, said method further comprising thesteps of: simultaneously cutting a plurality of said generallyconcentric grooves into said surface of said base for said polishing padsuch that radially inner most one of said multiplicity of generallyconcentric annular grooves has a radius of curvatures of 10 mm orsmaller.
 20. A method of producing a polishing pad according to claim19, wherein said turning tool comprises a plurality of said plate-likeshaped tool tips, said tool tips being fixedly arranged with each otherso as to aligned in a width direction thereof such that said cuttingparts of said tool tips cooperate to form a multiplicity of cuttingparts.
 21. A method of producing a polishing pad according to claim 20,wherein said turning tool further comprises a predetermined tool-tipholder to which said plurality of said plate-like shaped tool tips aredetachably fixed, said tool tip holder and said plurality of tool tipscooperate to constitute a tool unit.
 22. A method of producing apolishing pad according to claim 16, wherein said turning tool comprisesa plurality of cutting tips each having a cutting part and detachablyfixed to each other so that cutting parts of said plurality of cuttingtips cooperate to form a plurality of cutting parts which are arrangedin a predetermined direction with a pitch within a range of 0.2-2.0 mm,and wherein said circumferential grooves comprises a multiplicity ofgenerally concentric annular grooves, said method further comprising thesteps of: simultaneously cutting a plurality of said generallyconcentric grooves into said surface of said base for said polishing padsuch that radially inner most one of said multiplicity of generallyconcentric annular grooves has a radius of curvatures of 10 mm orsmaller.
 23. A method of producing a polishing pad according to claim16, wherein said turning tool is adapted to cut said circumferentialgrooves into said surface of said base for said polishing pad at a feedper revolution of 0.005-0.05 mm/rev in a depth direction of said base.24. A method of producing a polishing pad according to claim 16, furthercomprising the steps of: blowing ionic fluid toward a vicinity of saidcutting parts to neutralize said base of said polishing pad and chipswhich are electrically charged due to execution of said step of cuttingby the turning tool said circumferential grooves into said surface ofsaid base for said polishing pad.
 25. A polishing pad comprising: a basemade of a resin material; and circumferential grooves open in a surfaceof said base, said grooves having a width within a range of 0.005-1.0mm, a depth of 0.2-2.0 mm, and a pitch of 0.2-2.0 mm, wherein radiallyinner most one of said circumferential grooves has a radius of curvatureof not larger than 10 mm.
 26. A polishing pad according to claim 25,wherein radially outer most one of said grooves has a radius ofcurvature of not less than 100 mm.
 27. A polishing pad according toclaim 25, wherein said radially inner most one of said grooves has aradius of curvature of not larger than 10 mm, and said polishing pad hasa diameter which is made smaller than that of a working piece.
 28. Apolishing pad according to claim 25, wherein said circumferentialgrooves are spaced apart from each other at uniform pitch.
 29. Apolishing pad according to claim 25, wherein said base is a rigidurethane foam member, and said multiplicity of generally concentricgrooves are formed with a width of 0.20-0.30 mm, a depth of 0.1-1.0 mmand a pitch of 1.0-2.0 mm.
 30. A polishing pad according to claim 25,wherein said polishing pad is usable for polishing a substrate ofmultilevel interconnection type in which is formed an interconnect linehaving a width of 0.18 μm.
 31. A polishing pad according to claim 25,wherein said polishing pad is adapted to be directly placed on a platenof a polishing device for polishing semiconductor devices, withoutneeding an elastic layer interposed therebetween.
 32. A machine forgrooving a base for a polishing pad made of a resin material, saidmachine comprising: a bed; a platen including a hollow shaft membersupported by said bed via bearing so that said hollow shaft member isrotatably about a C-axis which is perpendicular to said bed; a suctionplate fixed to one of opposite axial end portions of said hollow shaftmember remote from said bed and formed with a plurality of through holesarranged evenly over an entire area thereof for attracting the base forthe polishing pad to be placed on said suction plate; drive mechanismfor rotating said platen about said C-axis and for positioning saidplaten at a suitable angular position; a gate-shaped column having twolegs which are opposed to each other with a spacing therebetween and across rail extending between and being perpendicular to said two legs,said gate-shaped column being movable in a direction of an X-axis withsaid cross rail extending across said platen; at least one saddlemounted on said cross rail so as to be movable in a direction of aY-axis extending along said cross rail; a tool rest mounted on saidsaddle so as to be independently reciprocally movable in a direction ofa Z-axis, said tool rest adapted to detachably hold a fixed toolcomprising a turning tool comprising a cutting part arranged to have atooth width within a range of 0.005-1.0 mm, a wedge angle within a rangeof 15-35 degrees, and a front clearance angle within a range of 65-45degrees; drive motors for moving and positioning said platen, saidcolumn and said saddle and said tool rest; and a numerical controlapparatus totally control an operation of said drive motor, wherein saidhollow shaft member of said platen is connectable to an air suctiondevice so as to attract said base for said polishing pad on said suctionplate by a suction force applied from said air suction device to saidbase for said polishing pad, and wherein said machine being operable tocut by said turning tool a multiplicity of generally concentric annulargrooves into a surface of said base for said polishing pad with saidbase for said polishing pad being attracted on said suction plate.
 33. Amachine according to claim 32, further comprising: an ion-blowing devicefor neutralizing said static electricity charged in said polishing padand chips, for separating said chips from said fixed tool and saidpolishing pad, wherein said ion blowing device includes an iongenerating device for generating ion, an ion extruding nozzle forextruding said ion toward said cutting part of said fixed tool, an airblowing device for blowing air together with said ion.
 34. A machineaccording to claim 32, wherein said tool rest detachably supports arotative tool selected from a group consisting of a milling cutter unitand a drill unit.
 35. A machine according to claim 32, wherein saidmilling cutter unit including at least one milling cutter fixedlysupported by a tool shaft extending along a center axis thereof, said atleast one cutter including a disk-shaped body member and a plurality ofcutting edges disposed at an outer peripheral portion of said bodymember at regular angular intervals, and each having a wedge anglewithin a range of 20-40 degrees, and a front clearance within a range of30-45 degrees, a tooth width within a range of 0.3-2.0 mm, and a sidecutting edge angle of 0-2 degree.
 36. A machine according to claim 35,wherein said machine comprises a plurality of said milling cutters whichare fixedly disposed onto said tool shaft such that said tool shaftextend through center axes of said plurality of said milling cutters andsaid plurality of milling cutters are spaced apart from each other in anaxial direction of said tool shaft at a uniform pitch of 0.1 or more.37. A machine according to claim 34, wherein said drill unit comprises asingle-spindle type or a multiple-spindle type drill unit, said drillunit including a drill having a drill diameter of 0.5-1.5 mm, a drilllength of 20-30 mm two cutting edges of helix angle of 1-10 degrees,said drill being a straight drill having no back-tapered portion atcutting edges thereof and having a shape edge that has a conical anglewith no chisel portion of 55-65 degrees.
 38. A machine according toclaim 32, further comprises a sequential control device adapted tocontrol operation of said drive motor in place of said numerical controlapparatus.
 39. A machine according to claim 32, wherein said machineincludes two of said saddles, wherein at least one of said tool holdersof said two saddles is adapted to detachably support said fixed toolcomprising said turning tool comprising a cutting part arranged to havea tooth width within a range of 0.005-1.0 mm, a wedge angle within arange of 15-35 degrees, and a front clearance angle within a range of65-45 degrees, and an other one of said tool holders of said two saddlesis adapted to detachably support said rotative tool selected from agroup consisting of said milling cutter unit and said drilling unit. 40.A machine according to claim 32, wherein said machine includes only onesaid saddle, said tool holder being adapted to interchangeably supportsaid fixed tool comprising the turning tool comprising a cutting partarranged to have a tooth width within a range of 0.005-1.0 mm, a wedgeangle within a range of 15-35 degrees, and a front clearance anglewithin a range of 65-45 degrees, or said rotative tool selected from agroup consisting of said milling cutter unit and said drilling unit.